It wasn’t only the Americans who were scrambling; the announcement came as just as much of a surprise to Mr. Trump’s Israeli visitors. Soon before they walked out for their joint news conference on Tuesday, Mr. Trump surprised Prime Minister Benjamin Netanyahu of Israel by telling him he planned to announce the Gaza ownership idea, according to two people briefed on their interactions.

Inside the U.S. government, there had been no meetings with the State Department or Pentagon, as would normally occur for any serious foreign policy proposal, let alone one of such magnitude. There had been no working groups. The Defense Department had produced no estimates of the troop numbers required, or cost estimates, or even an outline of how it might work.

There was little beyond an idea inside the president’s head.

Unlike major foreign policy announcements with past presidents, including Mr. Trump, the notion of the United States controlling Gaza had never been part of a public discussion before Tuesday.

But privately, Mr. Trump had been talking about U.S. ownership of the enclave for weeks. And his thinking had accelerated, according to two administration officials, after his Middle East envoy, Steve Witkoff, returned from Gaza last week and described the horrific conditions there.

But nobody — not in the White House, not the Israelis — expected Mr. Trump to roll out the idea on Tuesday until shortly before he did so. The idea was met with immediate opposition from the Arab world, including from Saudi Arabia, a key U.S. ally. And in comments to reporters on Wednesday, White House press secretary Karoline Leavitt tried to soften some of Mr. Trump’s statements.

While Mr. Trump had questioned why Palestinians would want to return to Gaza after being relocated and suggested the area could become a haven for tourists, Ms. Leavitt maintained that Mr. Trump simply wanted Jordan and Egypt to take in Palestinians “temporarily.” And she minimized the idea of U.S. financial investment, despite Mr. Trump positing a “long-term ownership” interest.

She also said the president had not committed to putting boots on the ground, although Mr. Trump had said: “We’ll do what is necessary. And if it’s necessary, we’ll do that.”

It is unclear whether Mr. Trump previously discussed the matter in any detail with the Israelis. A spokeswoman for the Israeli embassy did not respond to a message seeking clarity.

His presentation left more questions than answers, such as: How would this work? How many U.S. troops would be required to clear out Hamas and the mountains of rubble, and defuse all the unexploded ordnance? What would it cost to rebuild a demolition site the size of Las Vegas? How would seizing Palestinian territory be justified under international law? And what would happen to two million refugees?

In the hours after the announcement, senior administration officials were notably short on substantive answers. The reason for their evasiveness soon became clear: No actual details existed.

On Wednesday, Mr. Trump’s national security adviser, Mike Waltz, appeared on “CBS Mornings” to sell the Gaza idea. But it was clear from the conversation that this was less a plan than “concepts of a plan,” as Mr. Trump described his ideas for health care policy during the 2024 campaign. That plan never materialized.

“The fact that nobody has a realistic solution, and he puts some very bold, fresh new ideas out on the table, I don’t think should be criticized in any way,” Mr. Waltz said. “I think it’s going to bring the entire region to come with their own solutions if they don’t like Mr. Trump’s solution.”

Mr. Trump has been publicly pressuring the Jordanians and Egyptians for weeks to take in people from Gaza, but so far both countries’ leaders have refused. Forcibly removing the Gaza Palestinians would violate international law, but Mr. Trump said in his news conference on Tuesday that he expected they would be eager to leave the land because it was uninhabitable. Perhaps they could return eventually, he said.

He said all of that while standing beside Mr. Netanyahu, whose military campaign had obliterated much of Gaza after the Hamas terrorist attacks in Israel on Oct. 7, 2023 — creating the very conditions Mr. Trump was referring to.

“The U.S. will take over the Gaza Strip, and we will do a job with it, too,” Mr. Trump said. “We’ll own it and be responsible for dismantling all of the dangerous unexploded bombs and other weapons on the site. Level the site and get rid of the destroyed buildings. Level it out.”

Mr. Netanyahu, who has been trying to clear Hamas from Gaza since the Oct. 7 massacre of more than 1,200 people, looked pleased as Mr. Trump spoke.

Other U.S. officials were less thrilled about the proposal. Two people close to Mr. Trump insisted it was his idea alone; one said they had never heard him mention the involvement of U.S. troops before Tuesday.

Several senior officials, who spoke on the condition of anonymity to describe sensitive discussions, told The New York Times that they were still trying to figure out the genesis of the idea, and considered it fantastical even for Mr. Trump.

The concept is difficult to square with Mr. Trump’s criticisms of previous presidents for nation-building in the Middle East. His proposal that America take responsibility for one of the world’s worst disaster zones also came as he was shutting down the primary federal government agency responsible for foreign development assistance, U.S.A.I.D.

But Mr. Trump’s impulses have never been as anti-interventionist as the isolationists in his party would like them to be. When the Iraq war began, he initially cheered it before condemning it. In 2011, when he considered running for president, he said the United States should “take the oil” from Iraq, and he has promoted the idea of the U.S. military extracting critical minerals from overseas war zones.

In his second presidential term he has put his imperialist impulses on display. He has said he wants the United States to buy Greenland, refusing to rule out military force despite the existence of a U.S. base there. He has said he wants to take back the Panama Canal and that Canada should become America’s 51st state. He has said he thinks the United States should be entitled to Ukraine’s natural resources as repayment for all the military aid America has sent to help the Ukrainians defend themselves against the Russians.

Mr. Trump views foreign policy as a real estate deal maker. He has never cared about international law, never lectured autocratic leaders about human rights as other U.S. presidents have done.

Instead, for decades, he has viewed the world as a collection of countries that are ripping America off. He is preoccupied by the question of how to gain leverage over other nations, whether they are allies or adversaries. And he searches for ways to use American power to dominate other countries and to extract whatever he can. Mr. Trump does not believe in “win-win” diplomacy; all deals, whether in business or foreign affairs, have a clear winner and a clear loser.

Like Mr. Trump, his Middle East envoy, Mr. Witkoff, is a real estate developer and investor who has done business in the region. And Mr. Trump’s son-in-law Jared Kushner, another real estate investor who worked the Middle East portfolio in his first term, riffed last year about the incredible development opportunities presented by the Gaza waterfront.

Several advisers to Mr. Trump said they expected the Gaza ownership idea to die away quietly as it became clear to Mr. Trump that it was unfeasible. And that already seemed to be happening by Wednesday afternoon.

But Daniel B. Shapiro, who served as the U.S. ambassador to Israel under President Barack Obama, and more recently at the Pentagon, said even just floating the idea risked provoking more extremism: “This is not a serious proposal. The U.S. taking over Gaza, at massive cost in dollars and troops, is about as likely as Mexico paying for the wall or the United States seizing Iraq’s oil.”

“The danger is that extremists within the Israeli government and terrorists of various stripes will take it literally and seriously, and start to act on it,” he said. “It could imperil the further release of hostages, put a target on the back of U.S. personnel and undercut prospects of a Saudi-Israel normalization deal.”

When the Trump team hears warnings like this from former Democratic administration officials, they counter that Obama officials (although Mr. Shapiro was not among them) incorrectly warned that the Middle East would descend into violence after Mr. Trump moved the United States Embassy in Israel to Jerusalem in 2017. They also point out that it was Mr. Trump who delivered normalization agreements between Israel and four Muslim-majority states in his first term — an effort, known as the Abraham Accords, that the Biden administration tried unsuccessfully to expand upon.

Mr. Trump’s Gaza takeover idea delighted many on the hard right in Israel and some within America’s pro-Israel community. The Israeli government has long wanted to seize back Gaza from the Palestinians to ensure that the land cannot be used to launch terrorist attacks against Israel.

David Friedman, who served as Mr. Trump’s ambassador to Israel in his first term, was taken by surprise by the announcement but called the president’s idea “brilliant and out of the box creative and frankly the only solution I’ve heard in 50 years that has the chance of actually changing the dynamics in that troubled part of the world.”

Mr. Friedman said in an interview that the challenge his team had faced in the first Trump term was that “we never could answer the basic question, which is, is there anybody who can rule over Gaza that will not be a threat to the people in Gaza as well as to Israel?”

He said it was intolerable for Hamas or the Palestinians who supported it to remain in Gaza. Asked who would live there instead, Mr. Friedman said that after 15 years of rebuilding it would be a “market-driven process.”

“I know I’m sounding like a real estate guy,” he said, but he could not help but imagine the possibilities presented by “25 miles of sunset-facing beachfront.”

What Trump proposed for Gaza

Mr. Trump declared on Tuesday that the United States should seize control of Gaza and permanently displace the entire Palestinian population of the devastated seaside enclave.

Mr. Trump suggested the resettlement of Palestinians would be akin to the New York real estate projects he built his career on. “If we could find the right piece of land, or numerous pieces of land, and build them some really nice places with plenty of money in the area, that’s for sure,” he said. “I think that would be a lot better than going back to Gaza.”

“Everybody I’ve spoken to loves the idea of the United States owning that piece of land,” Mr. Trump added, “developing and creating thousands of jobs with something that will be magnificent.”

Mr. Trump’s aides on Wednesday walked back some of his comments, with the White House press secretary, Karoline Leavitt, saying that “the president has not committed to putting boots on the ground in Gaza.”

Real estate in Oman, Saudi Arabia and Dubai

The Middle East has in the past three years turned into the hottest spot for the Trump family in terms of new international real-estate deals. Most of these are so-called branding deals, which collectively earn the family tens of millions of dollars in fees in exchange for the right to use the name to help boost luxury condo, golf or hotel sales.

Recent agreements have been signed with a Saudi-based real estate company called Dar Al Arkan to build high-rise luxury apartments, golf courses or hotels in Oman, Saudi Arabia and Dubai.

“We are delighted to strengthen our ongoing relationship with the Trump Organization,” Ziad El Chaar, an executive with Dar Al Arkan’s subsidiary, said last year, in announcing one of the deals.

The project in Oman, which is the farthest along, involves the government of Oman itself, as it owns the land where the Trump golf course and hotel are being built.

Although the opening of the resort destination is still at least three years off, the Trump Organization has already raked in at least $7.5 million from the Oman deal, financial reports from the past two years show. Eric Trump and Donald Trump Jr. visited Oman this summer to check the project’s progress, visiting the site with Yousef Al Shelash, the chairman of Dar Al Arkan.

Dar Al Arkan itself has close ties with the Saudi royal family; the government there has been an important partner for the real estate company’s owners as they have built up their business.

The Trump family also examined a potential deal in Israel before the Oct. 7, 2023, attacks and remains interested in doing a project there, The Times previously reported. Mr. Trump’s son Eric Trump has said he intends to wait until the war ends before moving ahead.

Even before this recent burst of new Middle East deals, the Trump family already had an outpost in the region. Trump International Golf Club, Dubai, opened in 2017, shortly after Mr. Trump started his first term in the White House.

The partner in this Dubai club is DAMAC Properties, run by Hussain Sajwani, a billionaire real-estate executive who, Mr. Trump boasted in December, plans to invest billions of dollars in the United States to build data centers.

A partnership with LIV Golf

The Trump family also has been a key partner to LIV Golf, the upstart professional golf league financed by Saudi Arabia’s sovereign wealth fund. In April, for the fourth year in a row, the league is slated to hold one of its tournaments at the Trump National Doral near Miami.

LIV Golf pays the Trump family to host the tournament, which also drives thousands of customers to its restaurants and hotel rooms during the weekend event, scheduled for April of this year. Mr. Trump and his family own more than a dozen golf courses worldwide, all of which benefit from the media attention that the Saudi-backed tournament brings.

Mr. Trump has long sought to attract these kinds of tournaments to his golf courses, but had at least one major event canceled after a mob of his supporters attacked the Capitol on Jan. 6, 2021.

Jared Kushner’s investments

The president’s son-in-law, Mr. Kushner, runs a private equity firm called Affinity Partners that has raised $4.5 billion, mostly from sovereign wealth funds of the oil-rich nations of Saudi Arabia, Qatar and the United Arab Emirates, based on relationships he built as an adviser to Mr. Trump during his first term.

Mr. Kushner, who has said he does not plan to return to the White House, also has invested in at least two Israel-based businesses: Phoenix Holdings, an insurance company, and the car leasing division of Shlomo Holdings.

Mr. Kushner’s business partner at Shlomo Holdings is also a partial owner of Israel’s only domestic builder of warships. That puts him in business with executives who are also major shareholders in an Israeli military contractor whose vessels have been used in the war in Gaza, armed with American-made weapons.

It was Mr. Kushner who last year first floated the idea of considering Gaza as a potential real-estate development site. “Gaza’s waterfront property could be very valuable,” Mr. Kushner said last year during an event sponsored by Harvard’s Kennedy School of Government, suggesting that Israel “move the people out and then clean it up.”

Mr. Trump made his bombshell statement at the White House on Tuesday, during a visit by Prime Minister Benjamin Netanyahu of Israel — the first world leader the president has invited in his second term. Mr. Johnson noted the distinction offered to the Israeli leader and said it “is more than symbolism, but it is a symbol, and it shows the world that we’re not going to equivocate.”

Within hours, though, top Trump administration officials had begun trying to walk back some of the most explosive elements of Mr. Trump’s proposal, arguing that he had not committed to using American troops or funds for the rebuilding of Gaza, and suggesting that any relocation of Palestinians would be temporary.

Mr. Johnson, who spoke before the Trump administration’s apparent damage control efforts, defended Mr. Trump’s original comments, urging people to wait until more details emerged before judging the plan.

The speaker accused the Biden administration of appeasing Iran and its proxies — which include Hamas in Gaza, Hezbollah in Lebanon and the Houthis in Yemen — by encumbering Israel with restrictions and praised Mr. Trump’s new “bold” approach.

He also suggested that people “withhold judgment on all of it” for the time being, promising “more developments” to come. Mr. Johnson is expected to meet with Mr. Netanyahu on Thursday.

But some Republican lawmakers, even as they praised the president, seemed stunned by his proposal, which would appear to violate international law, and questioned its viability.

“Donald Trump is a visionary, a builder,” Senator Kevin Cramer, Republican of North Dakota, said. “He sees a beachfront property and has big ideas and floats those ideas.” But, he added, “the impracticality of it, I think, is hard to miss.”

Mr. Cramer noted that the United States had no claim to Gaza but suggested that the president “floats these big ideas” in order “to see what happens and see what shakes out.”

Similarly, Senator Mike Rounds, Republican of South Dakota, struck a conciliatory tone, saying that he understood the sentiments behind the proposal. Gaza has been decimated by more than 15 months of war between Israel and Hamas, a conflict ignited by the Oct. 7, 2023, attack Hamas led on Israel. Like Mr. Trump, Mr. Rounds suggested reconstruction would be easier if the two million Palestinians living in Gaza went elsewhere.

“The question is, how do you go about rebuilding a place in the middle of a construction thing?” Mr. Rounds said. “So I understand as a real estate developer, the president saying, if you move them out of the way, we can move and expedite the stuff on it.”

Other Republican lawmakers, when questioned about the plan on Tuesday evening, grimaced about the comments and declined to respond. Those who did speak appeared skeptical, though they maintained a cautious tone and did not outright dismiss the proposal.

Senator Josh Hawley, Republican of Missouri, said that he did not “think it’s the best use of United States resources to spend a bunch of money in Gaza,” adding that he would prefer that money “be spent in the United States first.”

Senator Lindsey Graham, Republican of South Carolina, said the plan “might be problematic,” but pledged to “keep an open mind.” He added that the United States would “see what our Arab friends have to say about” the president’s proposal.

Arab nations swiftly rejected the plan, which would put some of them — notably Gaza’s neighbors Egypt and Jordan — in an impossible position. Egypt and Jordan are among the top recipients of American military aid but dare not risk alienating their populations by appearing complicit in what many see as ethnic cleansing of Palestinians. Forcing Gazans out of their homes, many Arabs say, would doom a shared desire for Palestinian statehood and destabilize the entire Middle East in the process.

Democrats in Washington were far less circumspect in their outright rejection of the president’s idea.

“It’s a bizarre fantasy,” said Senator Tim Kaine, Democrat of Virginia. “It ain’t gonna happen.”

“Honestly, it was pandemonium,” said Thaer Ahmed, 38, a physician outside Chicago. “Everyone was texting each other. There were mixed emotions — some people thought it was hilarious, some people were furious. But nobody saw this coming.”

Mr. Trump made his proposal during a White House news conference as he stood beside Prime Minister Benjamin Netanyahu of Israel, who is the subject of an arrest warrant issued by the International Criminal Court for war crimes in the Gaza Strip.

The idea was met with immediate opposition from world leaders, who called it a breach of international law and a threat to regional stability in the Middle East. On Wednesday, the administration tried to walk back elements of the proposal, saying that Mr. Trump had not committed to sending U.S. troops to Gaza and that any relocation of Palestinians would be temporary.

In interviews, many Palestinian Americans said the idea of expelling millions of people from the Gaza Strip and placing it under American control was horrifying and absurd, and also unsurprising, given the broader context of Middle Eastern history.

“There’s a long list of adjectives we could run through,” said Yousef Munayyer, the head of the Palestine-Israel Program at the Arab Center Washington D.C., a think tank, when asked for his thoughts on the proposal. “Outrageous, criminal, harebrained. How much time do you have?”

But he noted that the idea of forcing Palestinians from their homes was in no way new.

“The region has suffered for decades from instability and conflict precisely because of the mass ethnic cleansing of Palestinians during the creation of Israel in 1948,” said Mr. Munayyer, referring to the expulsion and flight of some 750,000 Palestinians from the land. “That’s not lost on anyone there in the region.”

Just over two weeks ago, Mr. Trump and President Joseph R. Biden Jr. were celebrating a long-sought cease-fire deal between Hamas and Israel that was negotiated by advisers to both administrations in the closing days of Mr. Biden’s term.

But on Wednesday, all of that seemed very far away. Many Palestinians in the United States said they felt a deep sense of foreboding about the effect Mr. Trump’s comments could have on the fragile peace deal, under which Hamas has released Israeli hostages in exchange for Palestinian prisoners held by Israel. Negotiations over the cease-fire’s second phase only began earlier in the day on Tuesday.

And those interviewed said they were shocked by the ways that Mr. Trump’s proposal seemed to rewrite the recent history of the war in Gaza, which began in 2023 after Hamas and other groups killed roughly 1,200 people and took 250 hostages during a surprise attack on Israel.

In the war that followed, Israel displaced almost two million people, destroyed Gaza’s civilian infrastructure and killed more than 47,000 people, according to local health officials, whose count does not distinguish between civilians and combatants.

Zahra Sakkejha, 35, a Palestinian Canadian health care worker who lives in Los Angeles, said that it was impossible to overstate how painful it was to hear people in power keep saying that the solution to the Israeli-Palestinian crisis was simply to remove the Palestinians.

“It just hits the core wound of every Palestinian about the Nakba,” she said, referring to the events of 1948. “We can never be recognized for just wanting to live our life where we are from.”

Her family is from Jaffa, which is now a neighborhood of Tel Aviv. She does peace-building work with Israeli allies through an organization called Standing Together, but said that proposals like Mr. Trump’s made that task harder.

“We’re human beings, we have lives, we have the same hopes and dreams as anyone else,” she said. “So that’s part of the frustration, is that anytime that there’s mention of us as a people, it’s always in the context of either we’re terrorists or we’re a problem. We are like cattle they have to move around.”

Noreen Rashid, 22, of Rockaway, N.J., said she had long feared that the United States or Israel might take over Gaza. The proposal has made her reflect sadly on her last visit to see her relatives there, just one month before the war began.

“I saw the last of it, and the best of it,” she said. “Now I’m thinking about when I have children, and it’s an out-of-body experience to know they will never know Gaza — that it’s all going to be Trump villas.”

Laila Elhaddad, an activist and author who spent part of her childhood in Gaza and now lives in Maryland, said that watching Mr. Trump describe the removal of Palestinians from the “hellhole” of Gaza felt like stepping into “bizarro world.”

“The way Trump was speaking, it was like Palestinians in Gaza existed in a vacuum, when the person responsible for their suffering was standing there smirking to his left,” she said of Mr. Netanyahu. “They were acting like Gaza had the misfortune to be hit by some natural disaster.”

Before Mr. Netanyahu’s arrival, Ms. Elhaddad was part of a legal action by the Center for Constitutional Rights that called on the Justice Department to enforce the I.C.C. arrest warrant issued against the Israeli prime minister in November for war crimes and crimes against humanity in Gaza. The department did not enforce the warrant, and Ms. Elhaddad said she had not expected it to do so.

“Netanyahu said clearly at the beginning of the war that the goal was to make Gaza uninhabitable, and they destroyed anything that sustains life — the infrastructure, the schools and universities, the fishing fleets,” said Ms. Elhaddad. “So now is Trump proposing that he will finish their plans for them?”

That was also a fear for Taher Herzallah, 35, a graduate student in Minnesota. He said he “almost burst into laughter” when he heard the news of Mr. Trump’s proposal on Tuesday night because, he said, “it’s all one giant absurdity.”

But that sense of ridiculousness was tempered by darker feelings a day later.

Mr. Herzallah said he believed that the proposal amounted to an “ethnic cleansing” of the Gaza Strip, where he has already lost 33 family members during the war.

The announcement of the cease-fire provided his relatives with a brief moment of guarded optimism, he said. But that was extinguished on Tuesday.

“I feel a deep sense of dread of what’s to come,” he said. “My family has suffered unimaginable, unimaginable pain.”

Community leaders in Dearborn, Mich., a town whose largely Arab population has made it a frequent bellwether of Arab-American politics and popular opinion, said many residents were in a state of shock after Mr. Trump’s remarks.

But Mohamed Baja, a Trump supporter who works as the chef at a local restaurant, said maybe the president’s proposal had potential. “This violence has been going on for 60 to 70 years,” he said. “So maybe this one time things could work out. Maybe a couple of countries will take” Gaza’s inhabitants.

But, he added, he immigrated to the United States from Lebanon and is not Palestinian.

“It’s up to Gaza, not to me,” he said. “It’s not my land.”

Ernesto Londoño, Katherine Rosman, Sharon Otterman and Mary Chapman contributed reporting.

Already, the Hamas-led Oct. 7 attacks and Israel’s devastating response in Gaza had propelled the war into the center of the 2024 election, fracturing the Democratic Party and creating improbable new political alliances as some Arab American and Jewish voters shifted to the right.

But a new wave of recriminations arrived on Wednesday, even as skepticism abounded about the president’s far-fetched proposal and as top Trump administration officials walked back elements of the idea. Politicians and activists traded attacks and fought over whether this vision squared with Mr. Trump’s “America First” brand, which has always revolved around his promise to extricate the nation from foreign wars.

From the right, Mr. Trump received perhaps the sharpest Republican pushback of his nascent presidency, which has so far been defined by his party’s complete fealty to him. Some anti-interventionist lawmakers like Senator Rand Paul of Kentucky bristled at the idea. More hawkish leaders, like Senator Lindsey Graham of South Carolina, suggested that the proposal might simply be a nonstarter.

And on the left, some Democrats criticized the Arab and Muslim Americans, progressives and others who opposed Vice President Kamala Harris in protest of the Biden administration’s support for Israel — “is this what you wanted?” the argument went — as others vigorously defended that choice.

James Zogby, a member of the Democratic National Committee and a founder of the Arab American Institute, was unsparing toward those who advocated a protest vote.

“There was a need to recognize the danger of Trump and some folks in my community, some hustlers, were deliberately deluding themselves and others into thinking this was actually going to be a protest vote,” Mr. Zogby said. “It was a vote for suicide. They were helping to drive the car off the cliff and taking the community and the country with them.”

But in interviews on Wednesday, several Arab and Muslim American leaders or activists who voted for Mr. Trump stood by him. Some doubted that he would follow through on his Gaza proposal while also crediting him for the recent cease-fire, a product of collaboration between the current and previous administrations.

Mayor Amer Ghalib of Hamtramck, Mich., a Democrat who endorsed Mr. Trump last year, said on Wednesday that he did not believe the United States was prepared to force Palestinians out of Gaza.

“It’s all just talk,” Mr. Ghalib said as he waited for a call from the White House.

And Rabiul Chowdhury, a founder of Muslims for Trump, was willing to give Mr. Trump the benefit of the doubt, seeing him as a strong negotiator.

“Democrats and extreme left are trying to kind of use this to ignite our community, but we’re not falling for that trap — they’re still the worst in our eyes,” Mr. Chowdhury said. “We are finding our alliances through MAGA folks.”

There are many areas, he added, “where MAGAs and the Muslims align.”

Still others said that as Democrats try to rebuild a winning coalition, they should avoid casting blame for their 2024 defeat and try to win back voters who defected.

“I’m alarmed by the number of Democratic pundits who are going around with an ‘I-told-you-so’ approach to voters and communities who have voted for Democrats for 40 years,” said Waleed Shahid, a Democratic strategist who had urged the party’s primary voters to reject Mr. Biden. “I don’t think condescension and sneering is going to be helpful.”

Over the years, Mr. Trump’s vagueness and malleability on foreign policy have done little to resolve long-running tensions between Republican hawks and isolationists.

Secretary of State Marco Rubio praised the Gaza proposal, promising on social media that “the United States stands ready to lead and Make Gaza Beautiful Again.”

Senator Paul, a longtime opponent of U.S. intervention abroad, disagreed, suggesting that Mr. Trump threatened to break his campaign promises.

“I thought we voted for America First,” Mr. Paul said on X. “We have no business contemplating yet another occupation to doom our treasure and spill our soldiers blood.”

The conflict was the latest skirmish in a debate over foreign policy that Mr. Rubio and Mr. Paul have had at least since they ran for president in 2016.

Mr. Trump defeated them both, promising to shake up the Washington establishment on issues including international affairs.

Matt Brooks, the head of the Republican Jewish Coalition and a supporter of the administration, argued that Mr. Trump was fulfilling his campaign promises by rejecting what he described as “failed foreign policy.”

“The hallmark of President Trump is he does shatter old norms and existing norms when they don’t work,” Mr. Brooks said. Mr. Trump, he added, “is willing to take the risk.”

Asked if he would send U.S. troops, Mr. Trump said: “We’ll do what is necessary. And if it’s necessary, we’ll do that. We’re going to take over that piece.”

On Wednesday, Karoline Leavitt, the White House press secretary, told reporters something different.

“The president has not committed to putting boots on the ground in Gaza,” Ms. Leavitt said. She did not specify how the United States could take control of Gaza without military force, though she said Mr. Trump would be meeting with other leaders in the region to discuss next steps.

She also said that any displacement of Palestinians would be temporary. Mr. Trump had said he viewed the United States as taking “a long-term ownership position” in Gaza and that Gaza would become a place “not for a specific group of people but for everybody.”

Ms. Leavitt said: “The president has made it clear that they need to be temporarily relocated out of Gaza for the rebuilding of this effort. Again, it’s a demolition site right now. It’s not a livable place for any human being. And I think it’s actually quite evil to suggest that people should live in such dire conditions.”

Mr. Trump often makes comments that go beyond what his aides wish he would say and sometimes they try to walk them back. But the only statements that really matter are Mr. Trump’s.

Around the same time as Ms. Leavitt’s briefing, Marco Rubio, the secretary of state, also tried to walk back some of Mr. Trump’s comments. He suggested that Mr. Trump was only proposing to clear out and rebuild Gaza, not claim indefinite possession of it.

“The only thing President Trump has done — very generously, in my view — is offer the United States’ willingness to step in, clear the debris, clean the place up from all the destruction,” including unexploded munitions “so that then people can move back in,” Mr. Rubio said.

And, Steve Witkoff, the president’s special envoy to the Middle East, told Republican senators at a closed-door luncheon in the Capitol that Mr. Trump “doesn’t want to put any U.S. troops on the ground, and he doesn’t want to spend any U.S. dollars at all” on Gaza, Senator Josh Hawley of Missouri said.

A Republican senator asked Mr. Witkoff if Mr. Trump’s comments last night were made in the spur of the moment, and Mr. Witkoff replied that the administration had been “gestating on this plan for some time,” Mr. Hawley added.

Ms. Leavitt also said there was no written plan concerning Mr. Trump’s idea to take over Gaza before last night.

“The plan was written in the president’s remarks last night as he revealed it to the world,” she said.

Reporting was contributed by Catie Edmondson and Michael D. Shear in Washington.

The proposal

Mr. Trump had floated the idea of Palestinians leaving Gaza multiple times since taking office last month. His suggestion that they could be moved to Egypt and Jordan was rejected last week by those countries, along with a broad group of Arab nations.

On Tuesday evening, the president went even further. Speaking alongside Prime Minister Benjamin Netanyahu of Israel at the White House, Mr. Trump said the United States intends to seize control of Gaza, displace the Palestinian population living there and turn the devastated coastal enclave into “the Riviera of the Middle East.”

But he did not say how exactly he planned to do that — offering little detail on the logistics or extensive political maneuvering that would be required.

Regional complexity

A mass relocation of Gaza’s roughly two million inhabitants is a politically explosive idea in a region with a long and bloody history of forced resettlement.

While Mr. Trump framed the matter as a humanitarian imperative and an economic development opportunity, he effectively reopened a geopolitical Pandora’s box with far-reaching implications for the Middle East. Control over Gaza has been one of the major flash points of the Arab-Israeli conflict for decades — and to Palestinians and their allies, Mr. Trump’s proposal would constitute ethnic cleansing.

Many Gazans are descendants of Palestinians who were forced out of their homes during the wars surrounding Israel’s founding in 1948, a displacement that came to be known around the Arab world as the Nakba, or catastrophe. Now Mr. Trump is suggesting that they be displaced again — insisting that Palestinians would welcome it because “they’re living in hell” in Gaza.

“I would think they would be thrilled,” he said.

But the internationally backed Palestinian Authority rejected President Trump’s proposal, as did Hamas, which has ruled in Gaza for most of the past two decades and has begun re-establishing control there since a cease-fire deal with Israel took effect last month.

“Our people in Gaza will not allow for these plans to come to pass,” Sami Abu Zuhri, a senior Hamas official, said in a statement.

The cost

Mr. Trump likened his idea about displacement to the New York real estate projects on which he built his career. “If we could find the right piece of land, or numerous pieces of land, and build them some really nice places with plenty of money in the area, that’s for sure,” he said. “I think that would be a lot better than going back to Gaza.”

Where that money would come from, however, remains to be seen. Mr. Trump suggested that other countries in the region could finance the resettlement, but he offered no details.

He also did not say who would finance and build the gleaming and modern “Riviera” he was envisioning, either. Mr. Trump again suggested that other countries would pay for the reconstruction of Gaza — a project his Middle East envoy recently said would take 10 to 15 years — but also said he foresaw “a long-term ownership position,” without explaining what that meant.

The foreign ministry of Egypt, a key U.S. partner, said in a statement that aid and recovery programs for Gaza must begin “without the Palestinians leaving.” And King Abdullah II of Jordan on Wednesday rejected any attempt to displace Palestinians and annex their land, according to the Jordanian royal court.

The legality

Mr. Trump left a number of other basic questions unanswered, like how a U.S. takeover of Gaza would be enacted, and whether the use of force would be required. He conceded that American troops might be necessary.

But experts say that his proposal would unquestionably violate international law.

The Geneva Conventions — which both the United States and Israel have ratified — prohibit the forcible relocation of populations. Forced deportation or transfer of a civilian population is defined as a violation of international humanitarian law, a war crime and a crime against humanity.

It would be a further, severe violation for the United States to permanently take over the territory of Gaza, experts say. The specifics of that violation would depend partly on whether Palestine is considered a state, according to Marko Milanovic, a professor of international law at the University of Reading in England. The United Nations recognizes Palestine as a “permanent observer state” and 146 out of 193 U.N. member states recognize Palestinian statehood, but the United States does not.

The prohibition on one state annexing all or part of another state’s territory is one of the most important, foundational principles of international law. “There’s a clear rule,” Professor Milanovic said. “You cannot conquer someone else’s territory.”

It is rare for states to violate that rule. When they have, as in the case of Russia’s invasion of Ukraine, the response has been widespread global condemnation.

That could help explain why, by Wednesday afternoon, the Trump administration appeared to be trying to soften some of the president’s more problematic suggestions.

Speaking to reporters in Guatemala City during a trip to Latin America, Secretary of State Marco Rubio said Mr. Trump was only proposing to clear out and rebuild Gaza — not claim indefinite possession of the enclave.

“The only thing president Trump has done — very generously, in my view — is offer the United States’ willingness to step in, clear the debris, clean the place up from all the destruction,” Mr. Rubio said, so that “then people can move back in.”

It was an idea, Mr. Rubio added, that “people need to think about seriously.”

So it was a nightmare for the Palestinians’ closest Arab neighbors, Egypt and Jordan — and a dream for Israel’s far-right-dominated government — when President Trump proposed moving everyone out of the Gaza Strip and onto their soil, an idea he repeated in a White House news conference with Prime Minister Benjamin Netanyahu of Israel on Tuesday.

Egypt and Jordan have responded with categorical “nos” — even if their reasons aren’t all borne out of pure concern for the Palestinian plight: Cairo dreads what Palestinian refugees in Sinai would mean for Egypt’s security. Militants could launch attacks at Israel from Egyptian soil, inviting Israeli retaliation, or be recruited into the local insurgency in Sinai that Egypt has battled for years. Jordan’s king has to reckon with a population that is more than half Palestinian, so to accept more such refugees could further raise tensions.

That refusal has been backed up by political independents and opposition figures in Egypt, along with mouthpieces for the country’s authoritarian government, underscoring how the Palestinian issue can unify even the bitterest political opponents there.

Khaled el-Balshy, the editor of one of the few remaining Egyptian media outlets that are not pro-government and the head of the national journalists’ union, issued a statement on Wednesday calling Mr. Trump’s proposal “a clear violation of human rights and international laws.”

Moustafa Bakry, a loudly pro-government member of Parliament, suggested, without giving specifics, that Egypt could repel the displacement with force. “Egypt can move forward with other measures, because the Egyptian military can never allow this,” he said in an interview on Wednesday.

But Mr. Trump has shown little regard for the two countries’ concerns, their sovereignty or the idea of Palestinian statehood.

“They say they’re not going to accept,” Mr. Trump said of Egypt and Jordan during an earlier meeting with Mr. Netanyahu in the Oval Office. “I say they will.”

If he presses ahead with his proposal, the president may have ways of bending them to his will. Egypt and Jordan are among the top recipients of American military aid; Mr. Trump has mentioned the funding in recent weeks, without publicly threatening to pull it over the Gaza issue. With Egypt’s economy in crisis, the government is dependent on loans, including from the International Monetary Fund, in which the United States is the largest shareholder.

One reason the United States has given billions of dollars to Egypt and Jordan over the years is their special status as the first Arab countries to agree to peace treaties with Israel. The United States brokered those agreements after years of conflict, seeing them as key to the security of Israel. The arrangements have long been viewed as foundational to Middle East stability.

Egypt has cooperated closely with Israel on security in its restive Sinai Peninsula, which borders both Gaza and Israel. But while Egypt and Jordan are on speaking terms, and sometimes more, with Israel, their populations have never stopped seeing Israel as an enemy, especially after its most recent assault on Gaza.

Analysts say the incentives of keeping U.S. aid, which makes up a limited portion of each country’s budget, are minor compared to their fears of alienating their populations by appearing complicit in what many see as ethnic cleansing of Palestinians. Though the rulers of both countries frequently brook little dissent, often using repression to silence internal criticism, analysts say they cannot afford to ignore public opinion.

“It’s no joke going up against Trump, particularly for Egypt and Jordan,” said Paul Salem, the vice president for international engagement at the Middle East Institute in Washington. But since “this would really be a bridge way too far for much of public opinion,” he added, “there is no other option for an Arab leader. I don’t see what else they could do.”

For President Abdel Fattah el-Sisi of Egypt, the issue is particularly sensitive because he has tried to rally public support by painting himself as a champion of the Palestinians. Popular discontent over rampant inflation and government mismanagement had been growing before the war in Gaza began in October 2023, which allowed Mr. el-Sisi to regain some popularity with strong denunciations of Israel and promises to stand by the Palestinians.

But the shine wore off as the war went on and Egyptian social media swirled with reports of signs that Egypt’s leaders was cooperating with Israel. The government has arrested dozens of Egyptians who were protesting Israeli actions.

Mr. el-Sisi and his allies have tried to counteract the discontent, with Egyptian pro-government media frequently trumpeting Egypt’s role in delivering humanitarian aid to Gaza and pro-government politicians congratulating Mr. el-Sisi on personally brokering the recent cease-fire agreement. (Egypt served as one of the mediators on the deal, along with Qatar and the United States.)

Allowing Palestinian displacement into Egypt would “wreck the narrative of ‘I’m defending the country,’” said Maged Mandour, an Egyptian political analyst.

Egypt also sees the possibility of Palestinians settling en masse in Egypt as a serious security threat, government officials, diplomats and analysts say. Officials worry that members of militant groups among the forcibly displaced Palestinians could launch attacks at Israel from Egyptian soil, inviting Israeli military retaliation.

Egypt is also wary that Hamas, the Islamist group that controls Gaza, could stoke militancy and spread its influence in Egypt. Cairo has spent years trying to quash political Islamism and an insurgency at home.

Jordan, with its far smaller population — including many people of Palestinian descent — is perhaps even more vulnerable. Jordan’s monarchy has also had a tense history with militant Palestinian factions.

Far-right Israelis have long talked of Jordan as the place where Palestinians forced out of Gaza and the West Bank should make their homes, raising fears in Jordan that if people from Gaza are forced out, Israel would next turn to the West Bank.

Many, if not all, would likely be forced to go next door to Jordan, which is already unsettled by tensions between citizens who are of Palestinian descent and those who are not, analysts say.

Yet analysts said Israel’s hard-line government appeared so confident of U.S. support for its actions that it may be willing to destabilize relations with its neighbors.

But relying on U.S. backing to push through its ambitions over the strenuous objections of its neighbors will not be sustainable in the long run, said H.A. Hellyer, a senior fellow at the Royal United Services Institute in London and the Center for American Progress in Washington. He argued that “the only way for the Israelis to have long-term, sustainable security in the region is they have to actually integrate into the region.”

Some experts, including ones close to the Egyptian government, held out hope that Mr. Trump was merely taking an extreme starting position that would soften over negotiations.

As a businessman, “he will withdraw when it does not work out,” predicted Samir Farag, a former Egyptian military officer who often comments on Egyptian security affairs in pro-government outlets, in an interview on Wednesday.

But Mr. Hellyer said that the rhetoric from some people close to Mr. Trump who back the displacement plan and emphasize that even the West Bank should be considered Jewish land would make Arabs regard any Trump plan with extreme suspicion.

A much more limited version of the plan might be “theoretically acceptable” to Egypt and Jordan, he said, “but they’re ruining any possibility of that, because the framing of the whole thing now is, ‘We want to clear it out.’”

“I need to stay in my land — my life, my family and my memories are here,” said Mohammed Fares, 24, a resident of Gaza City who was displaced to the southern city of Khan Younis. “I have something in Gaza I can’t get anywhere else. I’ll stay, even through hell.”

Mr. Fares said he was staying at a relative’s home in Khan Younis because his family’s home in Gaza City had been destroyed and because there was little water available there.

About two million Palestinians remain in Gaza after a war that has reduced cities to rubble and killed tens of thousands of people. Israel waged a war against Hamas after the militant group led the Oct. 7, 2023, attack on Israel, which killed about 1,200 people.

Mr. Trump said that all Palestinians in Gaza should be moved to neighboring Arab countries such as Egypt and Jordan because of the devastation wrought by the war.

Palestinians blasted the notion of forced displacement, though some said they would be open to finding a more stable life outside Gaza.

“It’s unacceptable to expel people from their homes,” said Mukhlis al-Masri, 33, a resident of the northern town of Beit Hanoun displaced to Khan Younis. “But I never thought I would get to this place, where everything is a struggle.”

If he were able to move outside Gaza, Mr. al-Masri said, he would.

“Do I want to live through a tragedy for another 20 or 30 years?” he said. “Do I want to continue to live through hell? I can’t.”

Since a cease-fire between Israel and Hamas came into effect on Jan. 19, the entry of humanitarian aid to Gaza has surged but residents have said restoring a relative degree of normalcy still feels years away. The simplest of tasks before the war — charging a phone or bathing — have become daily ordeals.

In lieu of a shower, Mr. Mukhlis, his wife and their three sons lay a sheet of plastic across a classroom at a United Nations school and dump glasses of water on themselves, he said.

During the first eight months of the war, an estimated 100,000 people crossed into neighboring Egypt from Gaza, Diab al-Louh, the Palestinian ambassador to Egypt, said last year. While some of those people have stayed in Egypt, others have moved to other parts of the Arab world, sub-Saharan Africa, Europe and the United States.

But since Israel invaded Rafah, the southernmost city in Gaza, in May, almost all Palestinians have been barred from exiting the territory.

On Saturday, the first wounded and sick people passed through the Rafah border crossing between Egypt and Gaza in nearly nine months. But only a small number were permitted to leave.

Mohammed Abu Teir, 47, a father of five, said he had planned to sell his car, rent his home and move away from Gaza for years. But Mr. Trump’s statements had persuaded him to give up on those plans, he added.

“I refuse to leave,” he said. “I will live here, and I will be buried here. They talk about us as if we don’t exist, as if we can just be moved like pieces on a chessboard. But we are people — mothers, daughters, teachers and doctors.”

Other Palestinians criticized Mr. Trump’s claim that they would live in “peace and harmony” in new places outside Gaza.

Some Arab countries have seriously restricted the rights of Palestinian refugees. For example in Lebanon, they are barred from working in several professions.

“Arab countries consider us seventh-class citizens — they treat us as if we’re a threat,” said Abd al-Rahman Basem al-Masri, 27, a doctor from the central Gaza city of Deir al Balah. “Why should I leave the land of my fathers and forefathers for that?”

Steve Witkoff, Mr. Trump’s Mideast envoy, told reporters on Tuesday that he was set to meet Qatar’s prime minister, Sheikh Mohammed bin Abdulrahman Al Thani, in Florida on Thursday afternoon for further talks toward a permanent truce. Qatar and Egypt, alongside the United States, have been mediating negotiations between Israel and Hamas.

Mr. Trump’s remarks have now landed square in the middle of those sensitive negotiations. Analysts say it is far from certain that Israel and Hamas will advance from the initial six-week cease-fire — “phase one” — to the permanent truce — “phase two.”

The talks revolve around what terms would allow Israel to declare a permanent end to its war against Hamas and a full withdrawal from Gaza, including who will govern the enclave. In exchange, Hamas would release the remaining living hostages it has held since the Oct. 7, 2023, assault on southern Israel that set off the war in Gaza.

Israeli leaders have said they will not countenance Hamas rule in Gaza. Hamas has shown some willingness to abdicate responsibility for governing civil affairs in the enclave, but its leaders have said they will not cede military control there by disbanding the group’s armed wing.

Under Mr. Trump, the United States now appears to be throwing its weight behind an almost unheard-of and unworkable idea: moving the roughly two million Palestinians remaining in Gaza to neighboring countries and rebuilding the enclave under American control. Hamas has already rejected that proposal as a non-starter.

Prime Minister Benjamin Netanyahu of Israel, who stood alongside Mr. Trump when he announced his proposition for Gaza at the White House, said in a statement on Tuesday that he would convene the country’s security cabinet — a small group of senior ministers — to discuss Israel’s position in the “phase two” talks upon his return from Washington.

On Saturday, Hamas is expected to release the next group of hostages held in Gaza in exchange for Palestinians jailed by Israel. The two sides have conducted four hostage-for-prisoner swaps so far, prompting emotional scenes among both Israelis and Palestinians.

Hamas condemned Mr. Trump’s remarks but gave no indication that they would derail the upcoming exchange. The group is on Friday scheduled to announce the names of the next three hostages slated for release, after which Palestinian officials will receive a list of prisoners who will be freed from Israeli jails the next day.

Hamas is set to release at least 33 hostages as part of the first phase of the agreement with Israel, which the group’s leaders hope will lead to an end to the war in Gaza and leave them in power in the enclave they have ruled for the better part of two decades.

But if Israel and the United States move ahead with Mr. Trump’s ambitious plans — which would appear to leave no room for Hamas rule — that could lead the Palestinian militants to delay releasing further hostages as leverage, said Michael Milshtein, a former senior Israeli military intelligence official.

“We could see snares in the first phase — and we might never reach the second phase at all,” Mr. Milshtein said.