US President Donald Trump said on Friday he would soon decide on a proposed deal to extend the ceasefire with Iran, though the two countries still appeared to differ on significant issues that have been central to the conflict.

Trump said on Friday morning that he would meet in a secure White House room to make a "final determination" on the proposal, which would extend an early-April truce for another 60 days, giving negotiators time to forge a permanent end to the war.

A White House official said the meeting in the Situation Room lasted about two hours, but did not address whether Trump had made a decision.

"President Trump will only make a deal that is good for America and satisfies his redlines. Iran can never possess a nuclear weapon," the official said.

A senior Iranian source told Reuters an agreement was close but had not yet been approved.