Vice President JD Vance is leading the U.S. delegation in Switzerland.
President Donald Trump announced "major combat operations" against Iran on Feb. 28, with massive joint U.S.-Israeli strikes targeting military, government and infrastructure sites.
Following the announcement of a two-week ceasefire, initial U.S.-Iran talks in Pakistan in April failed to reach a peace deal. Trump later announced the open-ended extension of the ceasefire and the continuation of a U.S. blockade until negotiations concluded.
On Sunday, Trump announced that the U.S. and Iran had reached a "great deal." The memorandum of understanding was read to reporters on Wednesday, and the U.S. and Iranian presidents signed it that day, a White House official said.
Israeli Defense Minister Israel Katz said on Sunday that his country's military "will not withdraw from the security zone in Lebanon" and that the Israel Defense Forces are free "to act to eliminate threats."
"Preserving the lives of our soldiers and citizens is a top and absolute priority," Katz added in his statement.
-ABC News' Jordana Miller
Delegations from the United States and Iran arrived on Sunday at the Bürgenstock resort in Switzerland, where talks were set to begin.
Mediators from Pakistan and Qatar have also arrived at the resort, a luxury lakeside retreat outside Lucerne, the Swiss Ministry of Foreign Affairs said on Sunday.
Vice President JD Vance, along with the Trump administration’s envoys, Steve Witkoff and Jared Kushner, met on Sunday with Pakistani officials, including Prime Minister Shehbaz Sharif.
Vance had departed the U.S. on Saturday afternoon. He did not give formal remarks before meeting with Pakistani officials, who have served as key intermediaries for the U.S. in the negotiations. Rather, he thanked the Pakistani delegation for being there and asked how the pool reporters were doing after their flight, noting, "We'll speak to you guys later."
Esmaeil Baqaei, spokesperson for the Iranian foreign ministry, said on Sunday that the talks would focus on key paragraphs in the memorandum of understanding signed by both countries.
He said the "termination of the war on all fronts, including Lebanon," would be among the points discussed.
-ABC News' Rashid Haddou and Nicholas Kerr
Vice President JD Vance landed in Lucerne, Switzerland, just before 12 a.m. ET, according to his office.
No official schedule for his visit has been made public yet.
Vance is set to join Special Envoy Steve Witkoff and Jared Kushner in the region for expected talks with Iran.
Vice President JD Vance is en route to Switzerland where talks between the U.S. and Iran are expected to take place.
"I think we're going to hopefully make progress on the nuclear issue, make progress on the Lebanon ceasefire issue," Vance told reporters Saturday.
Vance will join Special Envoy Steve Witkoff and Jared Kushner who are already on the ground in Europe. Vance said Pakistan and Qatar would also be involved in the talks.
"I can only be there for a day or two," Vance told reporters in brief remarks before boarding his flight. "I think we're going to hopefully make progress on the nuclear issue, make progress on the Lebanon ceasefire issue. Those are the two big things that I think we're going to be focused on. I'm sure the Iranians are going to have issues they'd like to discuss as well."
