This photo taken on June 21, 2026 shows a sign outside Buergenstock mountain resort in central Switzerland. U.S. and Iranian delegates arrived on Sunday at Buergenstock mountain resort in central Switzerland for talks on implementing a memorandum of understanding signed by the two sides to reach a final deal. (Xinhua/Lian Yi) 

The Iranian delegation left negotiations with the United States in Switzerland on Sunday in protest of U.S. President Donald Trump's threat to launch further strikes against Iran, Iran's semi-official Tasnim news agency reported.

Tasnim cited a source close to the delegation as saying that "the negotiations stopped minutes ago."

Meanwhile, Iran's state-run Press TV quoted a source as saying that the delegation raised objections directly with the U.S. side, and "is assessing the conditions to give a proper response" to Trump's threat.

Earlier in the day, Trump wrote on Truth Social: "Iran must immediately stop their highly paid PROXIES in Lebanon from causing trouble. If they don't, we'll hit Iran very hard again, just like we did last week, only harder!!!"

Iranian Parliament Speaker Mohammad Bagher Ghalibaf, who heads the delegation, dismissed the threat, saying Iran's armed forces are ready to respond.

"They are better be careful about their comments ... Whatever they say, we are the ones who act," he said.

The talks in Switzerland focus on implementing Paragraph 13 of the recently-signed Iran-U.S. memorandum of understanding (MoU), which sets conditions for launching final agreement negotiations, including ending the war on all fronts including Lebanon, lifting the U.S. naval blockade, reopening the Strait of Hormuz, issuing waivers for Iran's oil exports, and releasing frozen Iranian assets, Iran's semi-official Fars news agency reported Sunday, citing Hossein Ghorbanzadeh, a member of the delegation.

Other provisions in the MoU will not be implemented until the war in Lebanon ends, Ghorbanzadeh said.

A draft for temporary sanctions exemption covering Iran's exports of oil and derivatives has been finalized and will soon take effect, he added.

The MoU, signed digitally on Thursday, was followed by a ceasefire agreement between Lebanon and Israel that took effect on Friday afternoon.

On Saturday, Israel's Prime Minister Benjamin Netanyahu and Defense Minister Israel Katz reportedly ordered the army to cease fire in Lebanon. But Katz said Sunday that the army will not withdraw from the "security zone" it holds in southern Lebanon.

Meanwhile, Lebanese sources have reported continued Israeli attacks on Lebanon over the past few days despite the ceasefire.