US officials are expecting Iran to respond to their proposal to end the crisis in the Strait of Hormuz as exchanges of fire in the disputed waterway threatened to collapse the month-long ceasefire.
Tehran has not indicated whether it could agree to the Trump administration's latest offer, which would see the US gradually lift its blockade and Iran re-open the strait over the next months.
Iran is continuing to review the proposal, the spokesperson for Iran's foreign ministry told Tasnim news agency on Friday, without providing further details.
Trump said Friday he was expecting a response "tonight" and threatened again to escalate the conflict if it did not respond positively.
"We may go back to Project Freedom if things don't happen," Trump told reporters in the White House, referring to the aborted attempt to escort stranded ships through the strait.
"It'll be Project Freedom Plus, meaning Project Freedom plus other things."
This came as the two countries exchanged fire in the strait and Iran launched attacks on the United Arab Emirates for the second day running.
The US struck Iranian tankers and military targets and Iran fired on three American warships in the strait, despite the ceasefire that came into force on 8 April.
Iran's Mehr news agency said one crew member was killed, 10 wounded and six missing in the US attack on one of the ships.
"Every time a diplomatic solution is on the table, the U.S. opts for a reckless military adventure," Foreign Minister Abbas Araghchi said.
The US military said it targeted the tankers because they were trying to break the blockade.
The two countries have engaged in a standoff over the crucial shipping corridor, which has been largely closed since the US and Israel launched the war 10 weeks ago.
Iran has insisted it should retain control over the strait as part of a peace settlement and wants to impose transit fees on ships to generate billions of dollars of revenues.
The closure has triggered a severe global energy crisis and provoked a US blockade on Iran's ports which it has refused to lift until Tehran agrees to a peace deal.
A recent CIA assessment suggested that the blockade would need to remain in place for another four months until Iran's economy faces crisis.
The US has also ramped up sanctions as part of its economic pressure campaign on Iran and its allies.
The Treasury on Friday imposed sanctions on another 10 companies and individuals, including some in China and Hong Kong, for providing Iran's military with weapons and raw materials used to manufacture its Shahed drones. China has vowed to ignore US sanctions over Iran, which were last week extended to Chinese refineries Washington says have bought Iranian crude.