France says it is “vital” that Vienna talks to revive the 2015 nuclear agreement “succeed” because if negotiations continue with the current speed there will be nothing left to negotiate.

French Foreign Minister Jean-Yves Le Drian made the remarks on Friday stressing that the pace of the talks is “way too slow” to be able to reach a result.

Le Drian said, “The choice is to return to the JCPOA agreement very quickly, or [to accept] a new [nuclear] proliferation crisis with Iran”.

He underlined that Iran is continuing its production of fissile materials and soon will be able to build a nuclear bomb, which makes any agreement useless.

Le Drian, however, added that if Iran wants to reach a deal, “we have the impression that there will be flexibility in the Americans' stance”.

He sounded less optimistic than EU foreign policy chief Josep Borrell who said that a renewed deal with Iran is still "possible" as the talks are advancing in a "better atmosphere".

"We're arriving at the end of a long process... there's a better atmosphere since Christmas — before Christmas I was very pessimistic. Today I believe reaching an accord is possible… in the coming weeks", Borrell said.

On Friday, chief negotiators of Iran and the three European participants in the Vienna nuclear talks returned to their capitals to hold consultations and update their respective governments.