Dismayed European allies have sought to salvage the Iran nuclear deal and preserve their Iranian trade after President Donald Trump withdrew the US from the landmark accord and ordered sanctions reimposed on Tehran.
"The deal is not dead. There's an American withdrawal from the deal but the deal is still there," French Foreign Minister Jean-Yves Le Drian said.
But Iranian President Hassan Rouhani, a pragmatist who helped engineer the 2015 deal to ease Iran's economically crippling isolation, told French counterpart Emmanuel Macron in a phone call that Europe had only a "limited opportunity" to preserve the pact.
Trump on Tuesday said he would revive US economic sanctions, which would penalise foreign firms doing business with Tehran, to undermine what he called "a horrible, one-sided deal that should have never, ever been made".
He said Iran would now either negotiate or "something will happen." It was not immediately clear what actions he was suggesting would take place.
Iran has drafted a "proportional" plan to cope with the US withdrawal, the official news agency, IRNA, reported.
The fruit of more than a decade of diplomacy, the nuclear agreement was clinched in July 2015 by the US, France, Britain, Germany, Russia, China and Iran.
It was designed to prevent Iran developing a nuclear bomb in return for the removal of sanctions that had crippled its economy, not least by Washington threatening to penalise businesses anywhere in the world that traded with Iran.
Trump complained that the deal, the signature foreign policy achievement of his Democratic predecessor, Barack Obama, did not address Iran's ballistic missile program, its nuclear activities beyond 2025 or its role in conflicts in Yemen and Syria.
His decision raises the risk of deepening conflicts in the Middle East, puts the US at odds with European diplomatic and business interests and casts uncertainty over global oil supplies.
The International Atomic Energy Agency (IAEA) has said Iran was honouring its commitments under the accord.
The chances of saving the deal without Washington depend largely on whether international firms are willing and able to keep trading with Iran despite the threat of US sanctions.
In a sign of what may be in store, Trump's ambassador to Berlin tweeted within hours of taking up his post that German businesses should halt activities in Iran at once.
Britain, France and Germany said they would do all they could to protect their business interests in Iran, yet it was unclear how much they can shield firms from US sanctions.
The Trump administration kept the door open to negotiating another deal, but it is far from clear whether the Europeans would pursue that option or be able to win Iran over.
Iran is the Organisation of the Petroleum Exporting Countries's third-largest member, pumping about 3.8 million barrels per day of crude, or just under 4 per cent of global supply. China, India, Japan and South Korea buy most of its 2.5 million bpd of exports.
Oil prices rose more than 2 per cent, with Brent touching a 3-1/2-year high.
