The US and Iran still need to work out several sticking points before an agreement on the war can be reached, Vice-President JD Vance has said, BBC reports.
Asked by the BBC if President Donald Trump was close to signing a deal, Vance said it was too early to say "when or if" the two sides would finalise an agreement.
The deal would reportedly extend the ceasefire for 60 days and launch talks on the future of Iran's nuclear programme.
Earlier on Thursday, US officials told the BBC that the two countries had agreed a framework of a deal, pending the approval of Trump and Iran's leadership.
But Iran's semi-official Tasnim news agency reported the deal had not been finalised or confirmed.
According to reports, the deal could allow "unrestricted" passage through the Strait of Hormuz, and that Iran would have 30 days to remove mines from the narrow shipping passageway.
The US would also lift its blockade, and issue sanction waivers to allow Iran to resume selling oil.
Axios, which first reported a tentative agreement between the US and Iran on Thursday, said Trump had been briefed on the proposal but did not immediately sign off on it and would take a couple of days to consider it.
One-fifth of the world's liquefied natural gas and oil normally pass through the Strait of Hormuz, and its closure has impacted global fuel trade.
Speaking on Thursday evening, Vance said negotiators were "going back and forth on a couple of language points", which include the "question of enrichment".
"We're not there yet, but we're very close and we're going to keep on working at it," he told reporters.
The US has long demanded that Iran stop producing highly enriched uranium and dispose of its existing stockpile, which in theory could be used to create nuclear weapons.
Vance struck an optimistic tone as he spoke to reporters in Washington DC, saying the US believed the Iranians were negotiating in "good faith".
