Both US and Iranian officials said progress was made during the first day of peace talks despite a rocky start to the summit in Switzerland.

Iranian officials initially abandoned talks in the wake of President Donald Trump's threat to 'blow the s*** out of them.' However, things eventually got back on track and a second day of meetings is scheduled.

A senior US diplomat claimed progress on multiple fronts, including the establishment of 'mechanisms' to ensure the Strait of Hormuz remains open and that a ceasefire in southern Lebanon holds. 

The diplomat, who spoke on condition of anonymity to brief journalists on the ongoing talks, said late Sunday that the Iranians remained on site and the negotiations were on. 

He said among the issues discussed was Iran’s messaging as it related to the Strait of Hormuz, which Iran’s military said it closed Saturday in response to continued fighting in Lebanon. US Central Command has disputed that Iran closed the strait again. 

Iranian Foreign Minister Abbas Araghchi wrote on X that 'tireless Pakistani and Qatari mediation has delivered major progress to end Lebanon War.' 

Mediators Qatar and Pakistan hailed what they called 'encouraging progress' made during the talks. 

The high-level negotiations seeking a permanent end to the Iran war concluded early Monday. 

Lower-level talks are planned for the rest of the week as Iran and the United States agreed to create a 'de-confliction cell' to address the fighting in Lebanon. 

Araghchi said the first 'real test' of negotiations would be whether that succeeded in halting the fighting. 

A member of Iran's negotiating team told state television that draft wording was reached about 'temporary sanctions waivers for oil and petroleum derivatives.' 

The Daily Mail has reached out to the White House for comment. 

Vance and US negotiators including Steve Witkoff and Jared Kushner, Trump's son-in-law, met with lead negotiator Mohammad Bagher Qalibaf and Araghchi for what Iranian state media said was about 80 minutes. 

The negotiations had a tense start Sunday after Trump threatened Iran with a restart to his bombing campaigns on the country through profanity-laced phone calls and posts on social media while Vance began negotiations.

Vance was attempting to downplay the intensity of the fighting in Lebanon during Sunday morning's negotiations, minutes before Trump renewed threats of bombing Iran if the country does not rein in Hezbollah and the militant group's strikes against Israel. 

Trump disclosed that he told Iranian officials: 'You close the strait and you won't have a country.

'You won't even make it back to your f****** country ... we'll take over the rest of the country,' he added, according to Fox News. 

'We may take over the Strait, if we have to. I'll blow the s*** out of them.' 

In a Truth Social post, the president wrote: '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!!!' 

'They would do better to be careful about their statements,' Iran's lead negotiator, Mohammad Bagher Qalibaf, said on X after Trump's comments. 

'Our armed forces are prepared to respond to them in a different manner. They may keep talking, it is we who act.'

However, a US official told the Daily Mail that discussions in Switzerland are expected to continue into the night with the Qatari and Pakistani delegations serving as mediators. 

Pakistan and Qatar after the meeting said lower-level technical talks would continue in Switzerland for the rest of the week. 

Such talks aim at producing the breakthroughs needed for high-level officials to return and sign agreements.

A senior U.S. diplomat engaged in the talks, speaking on condition of anonymity to describe private discussions, said the talks Sunday included clarifying what Iran meant by recent statements about the Strait of Hormuz. 

They also claimed Washington and Tehran have formed a 'line of communication' to manage the Strait of Hormuz to 'avoid incidents and miscommunication with the aim of safe passage for commercial vessels' during the ceasefire. 

Negotiators also discussed hopes that a ceasefire in southern Lebanon is enforced, along with 'robust' discussions on the nuclear issue. 

The parties 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.

The deal also calls for an end to fighting in Lebanon - a key demand from Iran listed in the first paragraph of the agreement. 

But only days after signing the agreement, it is being stress-tested after fighting escalated in Lebanon between Israel and the Iranian-backed militant group Hezbollah.

In response, Iran's military soon announced that the Strait of Hormuz was once again closed. The country said that resolving the situation in Lebanon would become a part of the negotiations in Switzerland. 

A renewed ceasefire in Lebanon, brokered on Saturday, appeared to be holding, and Israel's military said it would lift movement restrictions for residents near the border with Lebanon on Monday morning — another sign of calm.

But neither Israel nor Hezbollah is a signatory to the US-Iran deal, 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 attacks unless Israel commits to withdrawing. 

'The question before us now is how much more can we accomplish together? Can we turn over a new leaf?' Vance said as the talks began, and asked whether they could 'change relations in the Middle East permanently.' 

The Iranian delegation did not take part in speaking to assembled Western journalists ahead of the talks.

The agreement signed by Trump and Iranian President Masoud 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. 

The agreement 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 a year ago.

Pezeshkian, however, declared Sunday that 'we will never back down from the right to enrich uranium, and the other side is also forced to accept it,' according to Iran's state media.

Trump, in a telephone interview with Fox News, later warned that the Iranian president should watch what he says and threatened to take over Iran, in comments relayed by a Fox correspondent.

Iran had cautiously approached the talks given its previous experience with U.S. negotiations on the nuclear issue, which twice in the past year were interrupted by military strikes.

A CBS News Poll released Sunday revealed that 69 percent of Americans believe that Iran's nuclear program has not been permanently stopped, with 59 percent sharing a belief that Iran will not stop threatening its neighbors in the region in the coming months. 

Only 22 percent of respondents noted that they think the US is getting the better end of the deal, while 37 percent believe that it was better for Iran. 

Vance had originally been slated to be on the ground at the 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.

US Central Command has disputed Iran's claim that it once again shuttered the Strait of Hormuz and said US forces continued to monitor the situation to ensure traffic continues to flow through the waterway. 

The vice president has said that millions of barrels of oil have moved through the strait in recent days.

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 is actively considering a 2028 presidential campaign.

Trump and Vance have come under searing criticism from parts of their own party for the deal. 

Republican hard-liners have unfavorably likened 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 recent 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 US 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.'

Asian stocks were mixed Monday with markets in Japan and South Korea trading higher, while oil prices edged lower on fresh optimism over progress in US-Iran negotiations. US futures were trading lower.

Oil prices fell as talks progressed over a permanent end to the Iran war. Brent crude, the international standard, was trading 1.4 percent lower to $79.42 per barrel. It was at roughly $70 a barrel before the start of the war in late February.