Senior American and Russian officials agreed on Tuesday to establish teams to work toward ending the war in Ukraine and finding a path toward normalizing relations, in the most extensive negotiations between the two countries in more than three years.

After more than four hours of talks, Secretary of State Marco Rubio said that both sides had agreed to work on a peace settlement for Ukraine as well as to explore “the incredible opportunities that exist to partner with the Russians,” both geopolitically and economically.

A senior Kremlin official, Yuri Ushakov, said that both sides had “a very serious discussion on all the issues that we wanted to touch on,” including preparations for a summit meeting between President Trump and President Vladimir V. Putin.

The meeting was the latest striking swerve by the Trump administration in abandoning Western efforts to isolate Russia. Since Mr. Putin’s invasion of Ukraine, the United States and its Western allies had moved vigorously to punish Russia for causing Europe’s most destructive war in generations.

Instead, the talks on Tuesday showed that Mr. Trump was eager to work with Russia to end the war — an approach that would most likely fulfill many of Mr. Putin’s demands — and that he was prepared to cast aside the worries of American allies in Europe.

The comments suggested that apprehensions in Europe and Ukraine may only deepen that the United States and Russia could try to strike their own peace deal, sidelining Kyiv and American allies. And Russia appeared to have used Tuesday’s talks to cater to Mr. Trump’s interest in profits and natural resources, arguing that American oil companies and others stood to gain hundreds of billions of dollars by again doing business in Russia.

The meeting came less than a week after Mr. Trump’s lengthy phone call with Mr. Putin and took place at a palace in Riyadh, the capital of Saudi Arabia, whose crown prince, Mohammed bin Salman, has been seeking to elevate his country’s role on the world stage.

Michael Waltz, Mr. Trump’s national security adviser; and Steve Witkoff, the Middle East envoy and a longtime friend of Mr. Trump, joined Mr. Rubio for the meeting.

The Russian delegation included Sergey V. Lavrov, Russia’s foreign minister; Mr. Ushakov, Mr. Putin’s foreign policy adviser; and Kirill Dmitriev, the head of Russia’s sovereign wealth fund.

“We weren’t just listening to each other, but we heard each other,” Mr. Lavrov said afterward. “I have reason to believe that the American side started to better understand our positions.”

Mr. Dmitriev, who worked with Mr. Witkoff to broker the release last week of an American schoolteacher jailed in Russia, said he would seek to restart economic cooperation with the United States to “rebuild communication, rebuild trust, rebuild success.”

“U.S. oil majors have had very successful business in Russia,” Mr. Dmitriev said in a brief interview on Tuesday before the talks began, offering an example of how the countries could rebuild business ties. “We believe at some point they will be coming back, because why would they forgo these opportunities that Russia gave them to have access to Russian natural resources?”

Leading Western oil companies, including Exxon Mobil, joined many other businesses in pulling out of Russia three years ago amid outrage over Mr. Putin’s full-scale invasion of Ukraine.

Energy and economic ties were among the topics of the call between Mr. Putin and Mr. Trump last week, according to Mr. Trump and the Kremlin. After Tuesday’s meeting, Mr. Rubio described a three-step plan for what the United States and Russia planned to do next.

First, he said, both countries would negotiate how to remove restrictions placed on each other’s embassies in Moscow and Washington, which are operating with skeleton staffs after years of tit-for-tat expulsions.

In addition, he said, the United States would engage with Russia about “parameters of what an end” to the Ukraine war would look like.

“There’s going to be engagement and consultation with Ukraine, with our partners in Europe and others,” Mr. Rubio told reporters. “But ultimately, the Russian side will be indispensable to this effort.”

And finally, he said, Russia and the United States would explore new partnerships, both in geopolitics and in business. He described them as “the extraordinary opportunities that exist should this conflict come to an acceptable end.”

Russian commentators have expressed the hope that talks with the Trump administration and a peace deal in Ukraine could pave the way for the United States to lift the severe sanctions imposed by the Biden administration against Moscow.

Mr. Dmitriev said he would present the American delegation with an estimate showing that American companies lost $300 billion by leaving Russia.

“We need to put all facts on the table and then have a discussion based on facts, and not just ideological dogmas,” Mr. Dmitriev said. “We saw that President Trump is focused on having success.”

Tuesday’s discussions were the first time after Mr. Putin’s invasion in early 2022 that broad delegations of senior American and Russian officials are known to have met in person.

But in Europe and Ukraine, the news of Tuesday’s planned talks had been met with confusion and concern. While Mr. Rubio characterized the talks as preliminary, there was widespread criticism in Europe that Mr. Trump’s approach to Russia had not been coordinated with allies of the United States. And Ukrainian officials insisted they would reject any agreement about their country that was negotiated without their involvement.

“We cannot recognize any agreements made about us without us,” President Volodymyr Zelensky of Ukraine said Monday.

Mr. Zelensky has also been in the Gulf region this week, where several countries have sought to use their relationships with Moscow, Kyiv and the West to play roles as mediators in the Ukraine war. On Monday, Mr. Zelensky was in the United Arab Emirates to discuss prisoner exchanges and the return of Ukrainian children from Russia.

On Tuesday, Mr. Zelensky was set to meet with President Recep Tayyip Erdogan of Turkey in the Turkish capital, Ankara.

Ukrainian officials have also said that Mr. Zelensky will be in Saudi Arabia this week, but that Ukraine was not invited to the U.S.-Russia talks. Mr. Ushakov, the Kremlin foreign policy adviser, said there were no plans for a three-way meeting with the Ukrainians.

“We came here to hold negotiations with American colleagues,” he said.

For Saudi Arabia’s de facto ruler, Crown Prince Mohammed, hosting the talks has offered a major opportunity to solidify his status as a global leader with influence that extends beyond the Middle East.

The Saudis, in a Foreign Ministry statement, said they were welcoming the Russians and Americans “as part of the Kingdom’s efforts to enhance security and peace in the world.”

Like other countries in the Middle East, Saudi Arabia has avoided taking sides in the Ukraine war.

It has sent humanitarian aid to Ukraine while cultivating close ties with Russia. When a Ukraine peace conference was held in Switzerland last June that excluded Russia, Saudi Arabia and the neighboring United Arab Emirates refused to sign the final joint statement.

On Tuesday, two senior Saudi officials — Prince Faisal bin Farhan, the foreign minister; and Musaed al-Aiban, the national security adviser — were seated at the table with the American and Russian officials at the start of their meeting.

Andrew E. Kramer contributed reporting from Kyiv, Ukraine.

Khalil al-Hayya, Hamas’s chief negotiator, said in a speech on Tuesday that militants intend to hand over the remains of four Israeli hostages to Israel on Thursday in exchange for the release of Palestinian prisoners.

Mr. Hayya said that members of the Bibas family would be among the four bodies handed over to Israel on Thursday. The three remaining members of the Bibas family in Gaza include Shiri Bibas and her two children.

The Israeli prime minister’s office confirmed that the bodies of four Israelis would be returned on Thursday, but officials didn’t immediately respond to requests for comment about whether the Bibas family would be among them. The Israeli military had said until recently that there were grave concerns for the lives of Ms. Bibas and her children, though it had not confirmed their deaths.

Israeli officials had said earlier on Tuesday that they expected the remains of Israeli hostages to be returned on Thursday, though they did not specify that members of the Bibas family would be among them.

The number of living hostages scheduled to be released on Saturday will be increased to six from three, Mr. al-Hayya and the Israeli prime minister’s office said.

For years, European leaders have fretted about reducing their dependence on a wayward United States. On Monday, at a hastily arranged meeting in Paris, the hand-wringing gave way to harried acceptance of a new world in which Europe’s most powerful ally has begun acting more like an adversary.

President Trump’s plan to negotiate a peace settlement in Ukraine with President Vladimir V. Putin of Russia, with neither the Ukrainians nor Europeans invited to take part, has forced dazed leaders in capitals like Berlin, London and Paris to confront a series of hard choices, painful trade-offs and costly new burdens.

Already on the table is the possibility that Britain, France, Germany, and other countries will deploy tens of thousands of troops to Ukraine as peacekeepers. European governments are affirming the need for major increases in their military budgets — if not to the 5 percent of gross domestic product demanded by Mr. Trump, then to levels not seen since the Cold War days of the early 1980s.

“Everybody’s hyped up at the moment, understandably,” said Lawrence Freedman, emeritus professor of war studies at King’s College London. “What is clear is that whatever happens, Europe will have to step up.”

That could put its leaders in a difficult spot. While public support for Ukraine remains strong across Europe, committing troops to potentially dangerous duty on Ukrainian soil could quickly become a domestic political liability. Estimates on the size of a peacekeeping force vary widely, but under any scenario, it would be an extremely expensive undertaking at a time of straitened budgets.

President Emmanuel Macron of France, who first floated the idea of a peacekeeping force last year — to widespread skepticism in Europe — has been weakened since his decision to call parliamentary elections last summer backfired and left him with a fragile government.

Germany may not have a new coalition government for weeks after its election on Feb. 23. On Monday, its chancellor, Olaf Scholz, dismissed talk of peacekeepers as “completely premature” and “highly inappropriate” while fighting was still raging.

Prime Minister Keir Starmer of Britain, who does not have to face voters for four years, said that Britain was open to “putting our troops on the ground if necessary.” But former military officials said that after years of budget cuts, the British military was not equipped to lead a large-scale, long-term mission in Ukraine.

“Frankly, we haven’t got the numbers, and we haven’t got the equipment,” Richard Dannatt, a former head of the British Army, told the BBC. He estimated that Britain would have to supply up to 40,000 troops to a 100,000-strong force.

For some Europeans, it is too soon to talk about a post-American era on the continent. Mr. Scholz and Poland’s prime minister, Donald Tusk, warned leaders not to sunder the trans-Atlantic alliance, whatever the current tensions.

As a practical matter, a peacekeeping force would be difficult without logistical support from the United States. American security assurances, analysts said, were crucial to making it politically acceptable in European capitals, where some leaders will have to win approval from their parliaments. Mr. Starmer spoke of an “American backstop,” saying that was “the only way to effectively deter Russia from attacking Ukraine again.”

Professor Freedman said he believed that senior Trump administration officials like Secretary of State Marco Rubio and the national security adviser, Michael Waltz, understood those realities and were not bent on pulling America’s security umbrella from Europe. But he said that Mr. Trump’s goals were harder to decipher; his drive for untrammeled power at home has been deeply alarming to Europeans.

“In the past, you assumed that this was a serious, competent country,” Professor Freedman said. “It’s unnerving to think that might not be the case. There is a sense that the guardrails just aren’t there.”

At the Munich Security Conference this past weekend, the anxiety boiled over when Christoph Heusgen, who chairs the gathering, broke down in tears during his closing speech. It was a jarring display of emotion from a seasoned German diplomat, but Mr. Heusgen could be seen as merely channeling the feelings of his fellow Europeans.

His anguish was not prompted by the surprise news of Mr. Trump’s phone call with Mr. Putin nor by Defense Secretary Pete Hegseth’s warning that it was unrealistic for Ukraine to join NATO. Rather, it was in response to Vice President JD Vance’s blistering speech at the conference, in which he urged Europeans to stop shunning far-right parties and accused them of suppressing free speech.

“We have to fear that our common value base is not that common anymore,” Mr. Heusgen said.

Many Germans viewed Mr. Vance’s comments as brazen election interference. The vice president, who skipped a meeting with Mr. Scholz, did find time to meet with the co-leader of the far-right Alternative for Germany party, or AfD, Alice Weidel. Germany’s mainstream parties have refused to enter coalitions with the AfD, which German intelligence agencies classify as an extremist organization.

Mr. Trump, meantime, has threatened to hit the European Union with sweeping tariffs. That could damage the bloc’s economies, which would make it even harder to lift spending on defense. NATO’s secretary general, Mark Rutte, has called on the alliance’s members to increase their spending to “considerably more than 3 percent” of gross domestic product (the United States spends 3.4 percent).

In 2023, Germany spent 1.5 percent of its gross domestic product on defense, while France spent 2.1 percent and Britain 2.3 percent.

Beyond the political and economic provocations, European leaders are struggling to make sense of the Trump administration’s strategy for Ukraine. Mr. Hegseth’s remarks signaled a reduction in American support for Ukraine’s war goals — something that European leaders regret but privately acknowledge they share.

Yet Treasury Secretary Scott Bessent, on a visit to the Ukrainian capital, Kyiv, last week, suggested that the United States could supply a “long-term security shield” for Ukraine, provided it obtained access to the country’s valuable minerals. Mr. Trump’s announcement of negotiations between him and Mr. Putin blindsided European leaders and President Volodymyr Zelensky of Ukraine.

“A contradiction runs through the United States’ approach,” Nigel Gould-Davies, senior fellow for Russia and Eurasia at the International Institute for Strategic Studies, a research group in London, wrote in an online essay. “It has signaled that the U.S. alone will negotiate an end to the war but also that Europe alone must pay for and enforce an outcome it has not played a role in deciding.”

This assumes that Mr. Trump can strike a deal with Mr. Putin. Analysts note that the United States has already granted Russia two major concessions — ruling out Ukrainian membership in NATO and suggesting that it is unrealistic for Ukraine to reclaim all its territory — without receiving anything in return.

Some liken Mr. Trump’s approach to his nuclear diplomacy with North Korea’s leader, Kim Jong-un, during his first term. Meeting Mr. Kim in Singapore, Mr. Trump gave him a valuable concession — no more military drills between the United States and South Korea — without getting a reciprocal gesture. The negotiations petered out, and North Korea has yet to give up its nuclear arsenal.

In this case, analysts said, the odds against a quick breakthrough might spare European leaders from having to commit troops, at least for now.

“Unless the position on the ground improves greatly to Ukraine’s advantage, it’s hard to imagine Russia signing up to a deal that allows large numbers of NATO troops — including British ones — on its border,” said Malcolm Chalmers, deputy director general of the Royal United Services Institute, a research group in London.

Professor Freedman said that Mr. Trump would have to persuade Mr. Putin to agree to terms that are acceptable to Mr. Zelensky — an exceedingly long shot.

“We’re a long way from the circumstances where it makes sense,” he said of a peacekeeping force. “I can’t get past the incompatibility between what Trump can offer and what the Russians want.”