US Vice President JD Vance has told reporters that Washington was "not there yet" with Iran on an agreement but that the parties were close, adding that the US was in a position where it could substantially set back Tehran's nuclear programme.
The United States and Iran reached an agreement on Thursday to extend their ceasefire and lift restrictions on shipping through the Strait of Hormuz, pending US President Donald Trump's approval, many US and Middle East media outlets reported.
Vance said there were a couple of sticking points in talks with Tehran concerning its enriched uranium stockpile and the question of enrichment.
"It's hard to say exactly when or if the president is going to sign the MOU. We're going back and forth on a couple of language points. We've made a lot of progress here," Vance said.
"I can't guarantee that we're going to get there, but right now I feel pretty good about it," said Vance, who has played a key role in the negotiations.
Vance said the Iranians were negotiating in "at least so far in good faith" and both sides wanted to reopen the Straits of Hormuz — but there was still disagreement on Iran's stockpile of enriched uranium.
"There are a couple of issues on the nuclear stuff, the highly enriched stockpile, and also the question of enrichment," Vance said.
"Hopefully, we'll continue to make progress and the president will be in a position where he can endorse the agreement, but obviously that's still TBD," meaning to be determined, he added.
Trump and his team said from the start of the US-Israeli war on Iran that one of the prime reasons they undertook it was to ensure that Iran can never have a nuclear weapon.
But Vance, touting what he said the war had accomplished, told reporters that, "We’re in a position where we could substantially set back their nuclear programme, not just during the term of this president but over the long term."
Memorandum of Understanding
US sources had earlier confirmed a report by the Axios news outlet that the MOU would open the Strait of Hormuz but leave Iran's nuclear programme unresolved, with further talks to follow on the issue.
It reported that the 60-day deal will say that shipping through the Strait of Hormuz will be unrestricted, with no tolls or harassment and with Iran having to remove all mines within 30 days.
The US will in return lift its naval blockade on Iran's ports, but only in proportion to how much commercial shipping is restored, it said.
The memorandum will also contain an Iranian commitment not to pursue a nuclear weapon, Axios said. Among the first issues to be addressed is how to dispose of Iran's stocks of enriched uranium.
But Iran's Tasnim news agency, citing a source close to Tehran's negotiators, said the text had not been finalised and that mediator Pakistan would be informed if a deal was reached.
Iranian sources cited by local media said any deal would be complete only when announced by Tehran, not unilaterally by Trump.
US joined Israel in attacking Iran on February 28, with strikes quickly killing the longtime supreme leader, Ayatollah Ali Khamenei, and much of the other top brass, as well as hundreds of civilians.
But Iran quickly hit back by exerting control over the Strait of Hormuz, the narrow passageway through which one-fifth of global oil once sailed, and it has rained missiles and drones on US-allied Gulf Arab monarchies, shattering the oil-rich countries' hard-earned reputation for stability.
A fragile Pakistan-brokered ceasefire has been in place since April 7.
Islamabad has since intensified its efforts to bring an agreement between Washington and Tehran to end the war permanently.
