No 'Plan B' for Iran nuclear deal: France

France has no "plan B" for the Iran nuclear deal, French President Emmanuel Macron said on Fox News on Sunday interview, urging the US to stay in the agreement as long as there is no alternative option.

Macron made the remarks on the eve of his three-day visit to Washington on Monday, where he is expected to tackle deep differences over Iran and other key dossiers with US President Donald Trump.

Iran is set to top the agenda throughout the visit. Trump has set a 12 May deadline for the Europeans to "fix" the 2015 agreement that curbs Tehran's nuclear programme in exchange for sanctions relief, threatening otherwise to walk away. 

Iran said it is ready to relaunch its nuclear programme - which the West suspects is designed to produce an atomic bomb - if it fails.

Macron, who has emerged as Trump's privileged European partner, is urging him on behalf of Europe not to kill the deal.

"I don't have any Plan B for nuclear - against Iran," Macron told the Fox News Sunday television talk show before heading to Washington.

He argued that curbing Tehran's missile programme and containing its regional influence could be accomplished in addition to the 2015 accord.

Macron also cited the shared goal of reining in Iran as he argued for a long-term US commitment in Syria - where Paris and Washington have cooperated in fighting the Islamic State group and coordinated strikes on Syrian regime chemical weapons installations. 

"I think the US role is very important to play," he said. 

"Why? I will be very blunt. The day we will have finished this war against [IS], if we leave, definitely and totally, even from a political point of view, we will leave the floor to the Iranian regime, Bashar al-Assad and these guys."

I don't have any Plan B... against Iran.

Trump has threatened to abandon the accord unless European capitals agree to supplement it with tougher controls on Iran's missile programme and future ability to enrich nuclear fuel.

His partners maintain that the implementation of the agreement under the Joint Comprehensive Plan of Action (JCPOA) represents the best way to prevent Tehran from seeking the atomic bomb.

"We've been negotiating with the Europeans," a senior US official accompanying Acting Secretary of State John Sullivan told reporters. "We've made a great deal of progress but we're not there yet.”

A French diplomatic source told AFP that "several G7 ministers, led by the French, made a strong appeal to the United States... As it stands, we must not throw the JCPOA out with the bath water".

The Europeans are willing to work on a supplement to the deal which would not abrogate it in a bid to appease Trump.

They have promised to toughen controls on Iran's missile programme but "not give Iran a pretext to pull out, which would have disastrous consequences", the source said.

Agencies contributed to this report.