Negotiators for the US and Iran have agreed a framework of a deal that would extend their ceasefire for 60 days and launch negotiations on the future of Iran's nuclear programme, US officials say.
The agreement is yet to be approved by President Donald Trump or the leadership in Iran, the officials told the BBC.
But there were conflicting reports from Tehran, with Iran's semi-official Tasnim news agency quoting a source close to talks who said it had not been finalised or confirmed.
Both Iran and the US have accused each other of violating the fragile ceasefire in the past few days.
The two countries have resumed some hostilities, with Iran's Islamic Revolutionary Guard Corps (IRGC) saying it targeted a US base in the region, after fresh US strikes on Iran overnight.
On Wednesday, Iranian state media reported elements of what they described as an unofficial draft of a 14-point memorandum of understanding (MOU).
The report included the lifting of Washington's naval blockade of Iranian ports, the withdrawal of US forces from the "vicinity of Iran", and the restoration of non-military traffic through the Strait of Hormuz with Iran and Oman in control of the management and routing of vessels.
The White House called the purported MOU draft a "complete fabrication".
One-fifth of the world's liquefied natural gas and oil normally pass through the shipping channel, and its closure has impacted global fuel trade.
Both sides signalled progress had been made towards a deal late last week, prompting speculation an announcement was close.
Since the initial ceasefire between the US and Iran came into effect on 8 April, Trump has suggested - repeatedly - that the two sides are close to a deal and that negotiations are progressing, only to have any hopes of a negotiated end to the conflict dashed.
Talks that took place in Islamabad just days later, for example, ended without any substantive agreement.
In nearly every case, and as recently as Wednesday, Trump and other officials have warned that "option B", a return to combat operations, remains on the table.
Just last week, Trump told reporters that he had been an hour from ordering renewed strikes on Iran but ultimately held off at the request of US allies.
In a cabinet meeting on Wednesday, Trump said that talks were progressing but insisted that the Iranian proposal was "not there yet" and that work remained.
It is unclear what took place in the subsequent 24 hours, or when - or even if - Trump will give his final approval for the agreement to extend the ceasefire.
Doing so, however, would allow US and Iranian teams to discuss the far more complicated and technical issues at play, particularly about Iran's nuclear programme and its remaining stockpile of highly enriched uranium.
Trump had suggested that that US could take it, or, together with Iran, dilute it in place or in a third location.
Axios, which first reported the tentative agreement on Thursday, said that 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.
The confirmation from US sources of anonymously sourced Axios reporting on the contours of the agreement is rare, suggesting that the two sides may be closer to a deal than they were at any previous point during the more than six-week-old ceasefire.
Reports say 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.
Leading the White House briefing, Treasury Secretary Scott Bessent declined to confirm that an agreement had been reached.
"It's always a mistake to get out ahead of the president," he said, "and it is all going to be the president's decision".
Asked about whether any eventual peace deal includes "reconstruction" for Iran, he said: "'We've got to get to the deal before we get to the other side."
