French Foreign Minister Jean-Yves Le Drian said he had discussed the issue with his Chinese and German colleagues, hoping to avoid escalation of an already intense stand-off between Iran and the United States.

"France fully shares with Germany the central objective of de-escalation and preservation of the Vienna (nuclear) accord," Le Drian said in a statement.

With China, "we in particular noted our agreement... to urge Iran to avoid any new violation of the Vienna accord," he added.

The 2015 agreement negotiated between Iran and the UN Security Council permanent members -- Britain, France, China, Russia and the United States -- plus Germany offered Tehran relief from stinging sanctions in return for curbs to prevent it acquiring nuclear weapons.

US President Donald Trump withdrew from the deal last year and reimposed even more sanctions on Iran, which in turn has progressively dropped key commitments in the accord, including limits on uranium stock and enrichment levels.

Tehran recently announced that it would take a further step away from the accord in early January and this was widely expected to be announced on Monday.

The European Union, which helped broker the 2015 deal, has been trying to keep the accord alive despite the US withdrawal, but analysts say that now looks increasingly unlikely after the US killed Major General Qasem Soleimani, a key Iranian figure.