Iran's foreign minister announced advancements after the opening day of discussions between senior officials from Washington and Tehran concluded in Switzerland, despite an uneasy start involving threats from Donald Trump to resume strikes.

A joint statement issued by mediators Qatar and Pakistan indicated that the US and Iran have set out a plan toward a final agreement within 60 days. Technical sessions involving lower-level officials will proceed for the rest of the week, the statement noted, with the conflict between Israel and Iran-backed Hezbollah in Lebanon heading the agenda.

"Pakistani and Qatari mediation has achieved significant headway to conclude the Lebanon war," stated Abbas Araghchi, Iran's foreign minister, once the talks ended shortly after 3am local time (1am GMT).

The joint statement confirmed that the US and Iran would create a direct communication channel to prevent incidents in the strait of Hormuz and establish a de-confliction cell alongside Lebanon's government to secure compliance with ending military actions in Lebanon.

In a key step toward progress, the US Treasury is preparing a 60-day waiver to ease sanctions on oil, petrochemicals and derivatives. Iran indicated this would allow its central bank to sell oil to buyers, mainly China, and receive payments free from sanctions threats.

Qatar and Iran also signed a memorandum regarding the release of Iranian assets held in Qatar bank accounts due to US secondary sanctions. It remained unclear if the US had imposed conditions on how Iran could use those assets, such as limiting spending to humanitarian items.

These economic steps could ease some strain on Iran's currency markets and help moderate high inflation, currently the nation's primary domestic issue.

The mediators' joint statement centered on fresh implementation steps to put into effect the memorandum of understanding signed last week by Washington and Tehran over the coming 60 days, the period set for reaching an accord on Iran's nuclear program and sanctions relief.

Although the main talks with US vice-president JD Vance and Iranian chief negotiator Mohammad Bagher Ghalibaf were declared finished, lower-ranked officials will stay at the Swiss resort of Bürgenstock for continued technical work.

In his remarks, Araghchi noted that the first real test of the reached understandings would be the deconfliction approach for Lebanon, which has become the chief threat to last week's US-Iran agreement.

Over the weekend, Iran said it had restored its blockade in the strait of Hormuz in response to ongoing Israeli strikes on Lebanon and claimed Trump was permitting Israel to violate the MOU. The memorandum requires a ceasefire across all fronts, yet Israel killed more than 30 people in Saturday attacks in central and southern Lebanon.

Although the US military denied any closure of the strait, Trump reacted sharply to the threat on Sunday, stating: "You close it and you won't have a country. You won't even make it back to your fucking country."

The US president also commented on Lebanon, posting on social media: "Iran must immediately stop their highly paid proxies in Lebanon from causing trouble ... If they don't, we'll hit Iran very hard again."

Iranian state media reported that talks paused following the release of an insulting message from the US President. The Iranian delegation then consulted with Qatari mediators and departed the site, according to state outlets. Iran's semi-official Tasnim news agency added that the delegation declined to return to the main room but continued exchanging messages through Pakistani and Qatari mediators.

A senior US diplomat told reporters late on Sunday that the Iranians remained present and negotiations continued, the Associated Press reported.

Vance was accompanied by US special envoy Steve Witkoff and presidential son-in-law Jared Kushner. Iran was represented by Ghalibaf, the parliamentary speaker, and Araghchi. It was uncertain if Vance would remain for talks on Monday. The vice-president told US media he expected to stay only a day or two.

"The question before us now is how much more can we accomplish together? Can we turn over a new leaf?" Vance said at the start of discussions.

Vance and the US team aim to secure an accord on Iran's nuclear program. The MOU requires Iran to at least dilute its stockpile of highly enriched uranium, though several issues, including Tehran's future enrichment rights, stay unresolved.

Iran had wanted to delay nuclear talks until the US lifted its oil port blockade, issued a clear sanctions waiver for oil sales, and unfroze half of its estimated $24bn in overseas assets.

With most preconditions addressed, the mediators' statement showed that Iran would now allow some discussion on its uranium enrichment future and the dilution of its highly enriched uranium stockpile.

Araghchi identified the Lebanon crisis as the toughest remaining issue, calling the removal of conflict there the first genuine test of the agreement.