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 has 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.
On Monday, Iranian President Hassan Rouhani threatened "severe consequences" if the US withdrew from the deal.
The US president has long complained that the accord - signed by the US, Iran, Europe, Russia, China and Germany - does nothing to halt Iran's support for militant groups in the region such as Hezbollah.