Talks to end the Iran war could resume in Pakistan over the next two days, US President Donald Trump said on Tuesday, after the collapse of weekend negotiations prompted Washington to impose a blockade on Iranian ports.

Gulf, Pakistani and Iranian officials also said negotiating teams from the US and Iran could return to Pakistan later this week, though one senior Iranian source said no date had been set.

"You should stay there, really, because something could be happening over the next two days, and we're more inclined to go there," Trump was quoted as saying in an interview with the New York Post.

Iran's military command branded the blockade an act of piracy and warned that if the security of its harbours was "threatened, no port in the Persian Gulf and the Arabian Sea will be safe."

Despite the blockade, the fragile two-week truce agreed last Wednesday between Washington and Tehran remained in place, and signs that diplomatic engagement might continue helped calm oil markets, pushing benchmark prices below US$100 on Tuesday.

Iran has effectively shut the Strait of Hormuz, a crucial global waterway for oil and gas transport, since the war began on February 28. Roughly 5,000 people have died in the hostilities.

Talks in Islamabad last weekend did not yield an agreement, raising doubts over the survival of a two-week ceasefire that still has a week to run.

Iran's nuclear ambitions were a key sticking point. The United States had proposed a 20-year suspension of all nuclear activity by Iran, while Tehran had suggested a halt of three to five years, according to sources familiar with the proposals. The US has also pressed for any enriched nuclear material to be removed from Iran.

One source involved in the negotiations in Pakistan said backchannel talks since the weekend had produced progress in closing that gap, bringing the two sides closer to a deal that could be put forward at a new round of talks.

US Vice President JD Vance cautioned on Tuesday that there was a lot of mistrust between Washington and Tehran.

"You are not going to solve that problem overnight," Vance said during a Turning Point USA event.

Iranian negotiators wanted to make a deal, he said. "I feel very good about where we are," Vance added.

It was unclear what kind of nuclear deal could be quickly agreed by the US and Iran, given the complexity of the 2015 nuclear deal between Tehran and world powers that Trump withdrew from in 2018, and the likely need for monitoring and verification by the International Atomic Energy Agency.

Iran also wants international sanctions removed, a move the US could only pledge with broader support.

US Central Command said no ships made it past its blockade of Iranian ports in the first 24 hours it was in place, while six merchant vessels turned back.

Centcom said more than a dozen US warships were involved in the blockade, which only applies to ships going to or from Iran.

However, shipping data showed the blockade had made little difference to Strait of Hormuz traffic on Tuesday, with at least eight ships crossing the waterway.

The United States' Nato allies including Britain and France said they would not be drawn into the conflict by taking part in the blockade, although they have offered to help safeguard the strait when an agreement is in place.

China, the main buyer of Iranian oil, said the US blockade was "dangerous and irresponsible" and would only aggravate tensions. (Agencies)



Edited by Cecil Wong