OBBUERGEN, Switzerland (AP) — U.S. Vice President JD Vance and senior Iranian officials arrived in Switzerland on Sunday to formally launch negotiations over Tehran’s nuclear program and build out the fragile interim deal to end the war in Iran.The framework was signed last week, and now top U.S. and Iranian negotiators are in a 60-day sprint to reach an agreement on the technical details that hold massive implications for the world economy and global security.Yet only days after signing the agreement, it’s being stress-tested after fighting escalated in Lebanon earlier this week between Israel and the Iranian-backed militant group Hezbollah — and by the subsequent announcement by Iran’s military that it had again closed the Strait of Hormuz, the vital waterway that transits a fifth of the world’s traded oil and natural gas. A renewed ceasefire in Lebanon, brokered on Saturday, appeared to be holding up.Separate meetings kick off firstVance first sat down for talks with Pakistani Prime Minister Shehbaz Sharif and Staff Field Marshall Asim Munir, who has served as a key intermediary between the United States and Iran throughout the conflict.“What’s up, man! Good to see you,” Vance said as he warmly greeted Munir, who serves as Pakistan’s army chief.Mediators from Qatar were also on hand at the picturesque mountainside resort near Lake Lucerne on Sunday morning.Rafael Grossi, chief of the U.N. nuclear watchdog — the International Atomic Energy Agency — met with Swiss Foreign Minister Ignazio Cassis on the sidelines of the gathering.The agency had monitored the 2015 nuclear deal negotiated between the U.S. and Iran under the Obama administration. Trump withdrew the U.S. from the agreement in 2018.Iran’s main focus during negotiations on Sunday will be the ongoing war between Israel and Lebanon, Iranian Foreign Ministry spokesman Esmail Baghaei told Iran’s state news agency on Sunday.Iran is insisting that the deal’s implementation start with the part of the deal that calls for a cessation of all wars, including between Israel and Hezbollah. Baghaei said the U.S. “has been unable or unwilling” to hold Israel to the ceasefire.Iranian officials were to hold their own meetings with Pakistani and Qatari mediators before a planned four-way meeting that would include the U.S. negotiating team.Iran is cautiously approaching the negotiations given its previous experience with the U.S. negotiations on the nuclear issue, which twice in the past year have been interrupted by massive strikes against the country. “The implementation of any document is more important than its signing,” Baghaei said Sunday.But Iran’s president added that Iran will maintain its right to a nuclear program.“What is certain is that we will never back down from the right to enrich uranium, and the other side is also forced to accept it,” Iranian President Masoud Pezeshkian said on Sunday, according to Iran’s state media.STANSSTAD, SWITZERLAND - JUNE 21: U.S. Vice President JD Vance meets with Pakistan's Prime Minister Shehbaz Sharif for high-level talks aimed at advancing a deal to end the Middle East conflict at the Buergenstock Resort, Lake Lucerne on June 21, 2026 near Stansstad, Switzerland. Vance is visiting Switzerland for negotiations with Iran to end the war that have been delayed by Israeli strikes in Lebanon and over the opening the Strait of Hormuz. (Photo by Nathan Howard-Pool/Getty Images)Pool via Getty ImagesA delayed meeting is now back onVance had originally been slated to be on the ground at the picturesque Bürgenstock resort near Lucerne on Friday, but his departure from the United States was delayed after fighting escalated in Lebanon and Iranian officials canceled plans to attend the talks.U.S. Central Command disputed Iran’s claim that it had once again shuttered the strait and said U.S. forces continued to monitor the situation to ensure traffic continues to flow through the waterway. Vance has said that millions of barrels of oil have moved through the strait in recent days.Vance departed the U.S. just after Iranian state TV said Iran’s negotiators had arrived in Switzerland. Tehran’s negotiators include parliamentary speaker Mohammad Bagher Qalibaf and Foreign Minister Abbas Araghchi, along with central bank and oil officials.The vice president by special envoy Steve Witkoff and Jared Kushner, President Donald Trump’s son-in-law, for Sunday’s talks. Witkoff and Kushner were on the ground in Switzerland ahead of Vance to begin sifting through the technical details of the nuclear talks.Vance and his wife, second lady Usha Vance, arrived at Emmen Air Base outside Lucerne just before 6 a.m. local time, according to his office.While Vance said he planned to be in Switzerland for just “a day or two,” leaving much of the detailed negotiations to be spearheaded by Witkoff and Kushner, his role in the talks has heightened scrutiny of the vice president at a time when he’s actively considering a 2028 presidential campaign.Iran's Foreign Minister Abbas Araghchi (L) shakes hands with Switzerland's Foreign Minister Ignazio Cassis at the Burgenstock luxury hotel complex overlooking Lake Lucerne, Switzerland, on June 21, 2026, ahead of high-level talks aimed at advancing a deal to end the Middle East conflict. A new round of negotiations over the Middle East war was set to kick off on June 21, 2026 with Iranian negotiators arriving in the Swiss host city hours ahead of US Vice President JD Vance, even as Tehran said it was closing the Strait of Hormuz again over Israeli attacks in Lebanon. (Photo by Fabrice Coffrini / POOL / AFP via Getty Images)FABRICE COFFRINI via Getty ImagesThe deal has stirred much controversyTrump and Vance have come under searing criticism from parts of their own party for the deal, with Republican hard-liners unfavorably likening it to a nuclear agreement signed by the Obama administration that Trump and the GOP have insisted did nothing to actually terminate Iran’s nuclear program.The agreement signed by Trump and Iranian President Pezeshkian immediately allows Tehran to sell its oil freely and paves the way for Iran to tap into billions of dollars in assets that are currently frozen. It also calls for Iran to dilute its stockpile of highly enriched uranium, believed to be buried under nuclear sites that were targeted in U.S. strikes last summer.The agreement says commercial vessels can pass through the Strait of Hormuz for 60 days without a charge, but does not preclude future fees imposed by Iran. Trump made his own threat on Saturday to levy U.S. tolls on the strait if there is no deal with Iran in 60 days, insisting in a social media post that the money would be for “services rendered as the Guardian Angel to the countries of the Middle East.”The Trump administration has been working to reassure global markets that the Iran war has been merely a blip on oil prices, as Americans have complained the conflict resulted in hiking gasoline prices ahead of peak summer travel months. After the White House announced the deal a week ago, oil futures dropped almost 8% — and markets are expected to closely track the progress of talks when they open for trading on Sunday evening.Further complicating matters, neither Israel nor Hezbollah is a signatory to the deal between the U.S. and Iran, and Israeli Prime Minister Benjamin Netanyahu has vowed to keep his forces in southern Lebanon until any threat to Israel is eliminated. Hezbollah has refused to halt its attacks unless Israel commits to withdrawing from Lebanon.Fighting between Israel and Hezbollah in the initial days after the agreement between the U.S. and Iran killed 47 people in Lebanon, as well as four Israeli soldiers.___Kim reported from Washington. Associated Press writers Munir Ahmed in Islamabad, Amir Vahdat in Tehran, Iran, and Melanie Lidman in Tel Aviv, Israel, contributed to this report.RelatedIranj.d. vancePakistanswitzerland