A pending visit to Tehran by the European Union's coordinator for talks to revive the Iran nuclear deal is vital to its future, France said on Wednesday, questioning the new hardline Iranian administration's commitment to salvaging the pact.

Enrique Mora, the EU's political director, is due to hold talks on Thursday with members of Iran's nuclear-negotiating team four months after talks stalled between Iran and world powers, including the United States, to revive the 2015 deal.

"Through its statements and actions on the ground, the new Iranian administration of President (Ebrahim) Raissi raises doubts about its intention to return to the Joint Comprehensive Plan of Action (JCPoA)," French Foreign Ministry spokeswoman Anne-Claire Legendre told reporters in a daily online briefing.

"While refusing to negotiate, Iran creates facts on the ground that further complicate the return to the JCPoA. It is therefore in a context of crisis and at a critical moment for the future of the nuclear agreement that this trip by...Mora to Tehran takes place."

The Islamic Republic has repeatedly said it will return to the negotiations "soon" without giving any sense of what that actually means. Western diplomats have tentatively said a return to the Vienna talks may be possible before the end of October.

Legendre added that Tehran would also need to be clear about its intentions should it come back to the talks.

President Joe Biden aims to restore the deal but the sides disagree on which steps need to be taken and when.

Key issues include what nuclear limits Tehran will accept, what sanctions Washington will remove, whether there will be any guarantees and the prospect of follow-on talks on Iran's future nuclear program, regional and ballistic missile activities, diplomats have said.