Britain has watched President Trump’s tariffs with a mix of shock, fascination and queasy recognition. The country, after all, embarked on a similar experiment in economic isolationism when it voted to leave the European Union in 2016. Nearly nine years after the Brexit referendum, it is still reckoning with the costs.

The lessons of that experience are suddenly relevant again as Mr. Trump uses a similar playbook to erect walls around the United States. Critics once described Brexit as the greatest act of economic self-harm by a Western country in the post-World War II era. It may now be getting a run for its money across the Atlantic.

Even Mr. Trump’s abrupt reversal last week of some of his tariffs, in the face of a bond-market revolt, recalled Britain, where Liz Truss, a short-lived prime minister, was forced to retreat from radical tax cuts that frightened the markets. Her misbegotten experiment was the culmination of a cycle of extreme policies set off by Britain’s decision to forsake the world’s largest trading bloc.

“In a way, some of the worst legacies of Brexit are still ahead,” said Mark Malloch Brown, a British diplomat who served as deputy secretary general of the United Nations. Britain, he said, now faces a hard choice between rebuilding trade ties with Europe or preserving them with Mr. Trump’s America.

“The fundamental issue remains the breach with our biggest trading partner,” Mr. Malloch Brown said, adding, “If the U.K. ends up in the arms of Europe because neither of them can work with the U.S. anymore, that’s only half a victory.”

The first meeting between the United States and Iran over its expanding nuclear program on Saturday displayed a seriousness of purpose and an effort to avoid what neither side wants, another war in the Middle East. They will talk again next Saturday, but the hard work lies ahead, as hard-liners in both countries, and Israel, are expected to balk at most any deal.

If the first nuclear deal, reached in 2015, was prompted by Iran’s desire to rid itself of punishing economic sanctions, these talks have more urgency. Iran, battered by Israel and with its regional proxies diminished, still wants economic relief. But it also understands that the Islamic Republic itself is under threat and that President Trump, who pulled out of the first deal because he thought it was too weak, may not be bluffing about Iran’s facing “bombing the likes of which they’ve never seen before.”

And Iran’s supreme leader, Ayatollah Ali Khamenei, has given his negotiators at least one last chance to trade Iran’s nuclear ambitions for lasting security.

The talks in Oman also promised some efficiency. The 2015 deal was struck between Iran and six countries — the five permanent members of the United Nations Security Council plus Germany, with the European Union playing the role of intermediary — and took two years.

This time the talks are bilateral, with the Europeans but also Russia and China on the sidelines. And although the United States remains “the Great Satan” for Ayatollah Khamenei, it also holds the key to restraining Israel and securing any lasting settlement. While Iran insisted on indirect talks through Oman, and Mr. Trump on direct talks, the two sides managed to fudge the issue, with Mr. Trump’s special envoy, Steve Witkoff, talking directly to Iran’s foreign minister, Abbas Araghchi, as the meeting ended.

“This is as good a start as it gets,” said Ali Vaez, Iran project director for the International Crisis Group. “They could have stumbled, but they agreed to meet again, they met together at the end and they agreed on the ultimate objective.”

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Two Russian ballistic missiles slammed into a bustling city center in northeastern Ukraine on Sunday morning, officials said, killing at least 34 people in what appeared to be the deadliest attack against civilians this year.

The midmorning strike on the city of Sumy was the latest in a string of intensifying Russian attacks on urban centers in Ukraine that have inflicted heavy civilian casualties despite the Trump administration’s push for a cease-fire.

Officials said the city center was crowded with civilians out enjoying Palm Sunday, a Christian celebration popular in Ukraine, when the missiles hit. Lively streets were turned into scenes of carnage: Video of the aftermath showed mangled and bloodied bodies laying motionless, burning cars and debris covering the road as screams and sirens wailed in the background.

Two children were among the dead and at least 117 people were wounded, according to Ukraine’s emergency services.

“People were harmed right in the middle of the street — in cars, on public transport, in their homes,” the interior minister, Ihor Klymenko, lamented on social media.

Volodymyr Boiko, a 69-year-old Sumy resident, was riding in the back of a crowded bus when one of the missiles hit. He survived with cuts to his face, but said that those seated toward the front were not as lucky and took the full force of the blast. “It was just bodies, stacked on top of each other,” Mr. Boiko said.

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The Trump administration has revived talks with Saudi officials over a deal that would give Saudi Arabia access to U.S. nuclear technology and potentially allow it to enrich uranium, Energy Secretary Chris Wright said on Sunday.

The deal — which the Biden administration had pursued as part of a broader agreement for Saudi Arabia to establish ties with Israel — would enable the kingdom to develop a “commercial nuclear power industry,” Mr. Wright told journalists in Riyadh. He added that he expected to see “meaningful developments” this year.

“We’ve not reached the details on an agreement, but it certainly looks like there is a pathway to do that,” he said. “The issue is control of sensitive technology. Are there solutions to that that involve enrichment here in Saudi Arabia? Yes.”

Asked whether the talks were tied to Saudi Arabia’s agreeing to “normalize” diplomatic relations with Israel, Mr. Wright said only that “relationships are always package deals” and that there were many potential areas of cooperation between the two countries.

For years, Saudi Arabia has pressed the United States to help it develop a nuclear energy program, as Saudi officials look beyond oil to provide energy and diversify the economy. But talks on a nuclear partnership stalled, partly because the Saudi government refused to agree to conditions intended to prevent it from developing nuclear weapons or helping other nations do so.

A crucial sticking point, for example, has been whether the kingdom would import uranium or enrich it domestically, which could theoretically enable it to produce uranium for use in nuclear weapons.

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The Israeli military struck and destroyed part of a hospital in northern Gaza early on Sunday morning, shortly after telling patients and staff to evacuate the site. The attack came hours after the Israeli government announced that its troops fighting elsewhere in the territory had expanded their occupation of the southern Gaza Strip, severing links between two strategically located Palestinian cities.

No one was killed in the attack on the Ahli Arab Hospital, but a child being treated for a head injury died because of the rushed evacuation, according to a statement released by the Anglican Church in Jerusalem, which oversees the medical center. The strike destroyed a laboratory and damaged a pharmacy, the emergency department and a church at the hospital compound in Zeitoun, the statement added.

The hospital had become one of the last mainstays of the health care system in Gaza, where medical centers have been frequently damaged and besieged during the war that began with the Hamas-led October 2023 attack on Israel. The World Health Organization reported last month that 33 of Gaza’s 36 hospitals had been damaged during the war, and only 21 remained partly functional. The W.H.O. also warned on Saturday that hospitals in Gaza face a looming medicine shortage because Israel has blocked aid deliveries for six weeks.

The Ahli Arab Hospital compound was first hit less than two weeks into the war, when a missile hit a parking lot on the site where dozens of displaced families were sheltering. Hamas blamed the strike on Israel, before Israel said it was caused by an errant rocket fired by Palestinian Islamic Jihad, a group allied with Hamas. U.S. intelligence officials later said they had “high confidence” in the Israeli account.

The Israeli military acknowledged responsibility on Sunday for the latest strike on the hospital, saying without offering evidence that the site had housed a Hamas command center. Both the military and the Anglican Church said that Israeli soldiers had called the hospital to order its evacuation before the strike. Neither the hospital authorities nor Hamas responded to questions about whether the hospital had been used by Hamas fighters.

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A Gaza paramedic for the Palestine Red Crescent Society who has been missing since Israeli forces ambushed a group of ambulances and other aid vehicles in late March is in Israeli custody, the Red Crescent and the International Committee of the Red Cross said on Sunday.

Israeli forces killed 15 other rescue and aid workers in the same attack, buried their bodies in a mass grave and crushed their ambulances, their fire truck and a United Nations vehicle — actions that have drawn international condemnation and scrutiny.

Witnesses have said that Asaad al-Nasasra, 47, the paramedic who disappeared after the March 23 attack, survived but was detained and taken away by Israeli soldiers. But there had been no official word of his whereabouts until Sunday, when the Red Crescent said the I.C.R.C. had notified it that he was being held by Israel.

The Red Cross said in a statement that it had received information that Mr. al-Nasasra was being held “in an Israeli place of detention.”

Asked for comment, the Israeli military replied with a statement that it had released last week saying that it was still investigating the attack. It has said it will not comment further until the investigation is complete.

The Israeli military has offered changing explanations for why its troops fired on the emergency vehicles, first saying that they had been “advancing suspiciously” without their lights on until a video of the attack contradicted that account. It initially said nine of those killed had been operatives from Hamas or Palestinian Islamic Jihad, another militant group, before saying, without providing evidence, that six operatives were killed in the attack.

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As China faces off with the United States over a punishing trade war, it is under pressure to shore up its friendships around the world, starting with its neighbors in Southeast Asia. But its relations there are complicated.

China’s leader, Xi Jinping, will be testing these ties this week as he visits Vietnam, Malaysia and Cambodia in the hope of blunting the effect of huge tariffs imposed by President Trump on Chinese exports to the United States.

Mr. Xi is likely to cast China as a reliable global partner in contrast to the unpredictable United States of President Trump, whose on-again, off-again tariffs have upended financial markets and confounded governments. While in Vietnam, for instance, Mr. Xi is expected to oversee the signing of around 40 agreements, including deals that would advance plans for Vietnam to accept Chinese loans for part of a $8.3 billion railway connecting northern Vietnam with China.

But his visit also points to a diplomatic tightrope that countries like Vietnam and Malaysia must walk as the Southeast Asian nations try to negotiate with the Trump administration for a reprieve from the tariffs.

Mr. Xi’s tour will start in Vietnam on Monday, followed by a three-day visit to Malaysia, ending the week in Cambodia.

Trade at the Forefront

For the past decade, Beijing has engaged in a huge push to extend its economic and political influence across Southeast Asia. China is now the region’s most important trading partner. Senior officials, including Mr. Xi, regularly travel there.

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The Democratic Party in Hong Kong was for decades the city’s largest opposition party. It led protests demanding universal suffrage. Its lawmakers sparred with officials in the legislature about China’s encroachment on the region.

It was born in the 1990s of an audacious hope: that opposition politicians and activists could pressure Hong Kong’s iron-fisted leaders in Beijing to fulfill their promise of expanding democratic freedoms for the city of several million people.

On a rising wave of demands for democracy, the party grew to more than 1,000 members at its height in 2008. Its effort to maintain a moderate stance drew criticism, including from within its own ranks, from those seeking to push harder against Beijing. Yet moderation could not save the party’s leaders from being caught in the dragnet as China tightened its control over Hong Kong.

Now it is disbanding, one more casualty in Beijing’s suppression of Hong Kong’s once-vibrant political opposition.

Its leaders have been arrested and imprisoned on national security charges. Its members are effectively barred from running for local office and routinely face harassment and threats. Raising money is hard.

“We have not achieved what we set out to do,” Fred Li, a founding member of the party who was not part of the most recent leadership, said in an interview, referring to democratization under Chinese rule. “Without money or resources, we can’t even survive ourselves.”

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