The sharp words stand in stark contrast to the optimistic comments from Vice President JD Vance ahead of the talks in Bürgenstock, Switzerland, on Sunday afternoon.
"We have already made great progress in the last few hours and I expect further progress in the coming hours," Vance said, according to CNN.
A while later, his boss, Donald Trump, who is back in the US, took to Truth Social, where he threatened Iran.
Trump's threat
"Iran must immediately stop its well-paid proxies in Lebanon from causing trouble. If they do not, we will strike them again very hard, just like last week, only harder," he wrote, where proxies refer to the Shiite militia Hezbollah.
This prompted Iran's chief negotiator, Mohammad Bagher Ghalibaf, to say that threats will not be factored into the negotiations and that Tehran is prepared to defend itself in the event of any attack.
"They would have been better served by being careful with their statements. Our armed forces are ready to respond," said Bagher Ghalibaf, according to AFP.
Information on paused negotiations
On Sunday evening, media reports emerged that the Iranian delegation had paused or left the negotiations after Trump's threat.
Iranian state television reported that the Iranian delegation had left the building where the talks were taking place, according to AFP, while CNN, citing an Iranian source, said the negotiations had stalled but had not ended.
Ahead of the meeting, the Iranian Foreign Ministry said that the conflict between the Shiite militia Hezbollah and Israel in Lebanon would be at the top of the agenda and that Iran would not enter the negotiation phase of the final agreement unless the conflict there ends.
Iran's frozen assets and its oil sales are also high on the list.
Iran said on Saturday that it had closed the Strait of Hormuz again in response to the Israeli attacks. US President Donald Trump has threatened to impose tariffs on the strait if a final agreement with Iran is not reached within 60 days.
For the United States, the issue of Iran's nuclear program is of great importance. As Vance left the United States to fly to Europe late Saturday night, he told reporters that he hoped for "progress on the nuclear issue."
