US President Donald Trump and his French counterpart Emmanuel Macron have suggested there could be a new agreement on Iran's nuclear programme.
After talks in the US, Mr Trump, who is sceptical of an accord that was struck in 2015, spoke about "doing a much bigger, maybe, deal".
Mr Macron said a new pact must cover Iran's ballistic missile programme and its role in the Middle East.
Iran warned of "severe consequences" if the US withdraws from the deal.
In 2015, Iran agreed to mothball its nuclear programme in return for an easing of economic sanctions on Iran.
The US president has been threatening to reject an extension of the Obama-era nuclear pact reached between Tehran and world powers by a 12 May deadline.
Mr Macron had been lobbying Mr Trump to stick with the deal, saying there was no better option.
Germany's Chancellor Angela Merkel is due to visit the US on Friday to make a last-minute bid to dissuade Mr Trump from potentially torpedoing the agreement.
Iranian Foreign Minister Javad Zarif was quoted as saying that Tehran would "most likely" abandon the accord if the US pulled out.
What did Trump and Macron say in Washington?
"I think we will have a great shot at doing a much bigger, maybe, deal," the US president said, adding that any new agreement must be built on "solid foundations".
"They should have made a deal that covered Yemen, that covered Syria, that covered other parts of the Middle East," said Mr Trump, referring to the 2015 accord which he described as "insane".
Meanwhile, Mr Macron agreed that Tehran's influence in the region must be part of negotiations.
He also stressed that - as well as controlling Iran's nuclear programme for the next decade as envisaged by the current agreement - a fresh deal would need to cover its nuclear activities longer-term, as well as its ballistic missile programme.
And he talked about working with President Trump to build a "new framework" in the Middle East - and especially in Syria.
Mr Macron said he did not know whether Mr Trump would extend the 12 May deadline, adding: "I can say that we have had very frank discussions on that, just the two of us."
Mr Trump earlier warned Iran against resuming its nuclear programme.
"They're not going to be restarting anything. They restart it they're going to have big problems, bigger than they've ever had before."