US and Iranian negotiators have agreed on a framework for a 60-day ceasefire extension deal but it still needs President Donald Trump's approval, US sources told AFP on Thursday.

The sources confirmed a report by the Axios news outlet that the two sides had reached agreement on a memorandum of understanding to prolong the truce and launch negotiations on Iran's nuclear program.

There was no immediate confirmation from Trump himself, or from Iran.

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, Axios reported.

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.

Trump has repeatedly insisted that Iran cannot have a nuclear weapon under any deal to end the war that the US and Israel launched on February 28. A fragile ceasefire has been in place since April 7.

The US president said on Wednesday that he was "not satisfied" yet with Iran's offers and warned that he could "finish the job" militarily.

Washington and Tehran both accused each other of violating the truce earlier on Thursday following an exchange of fire.