PARIS -- France on Friday urged Iran to curb nuclear activities of 鈥渦nprecedented gravity鈥 as U.S. and European envoys met to discuss efforts aimed at reviving the troubled 2015 Iran nuclear deal.

U.S. envoy Robert Malley joined counterparts from France, Britain and Germany at the meetings in Paris, at what the French Foreign Ministry called a 鈥渃ritical time鈥 in efforts to salvage the accord.

鈥淚t is urgent and crucial for Iran to end the activities of unprecedented gravity that it is conducting in violation of the (agreement) and to immediately resume full-fledged cooperation鈥 with the International Atomic Energy Agency, Foreign Ministry spokesperson Anne-Claire Legendre said in an online briefing.

In Washington, State Department spokesman Ned Price told reporters the U.S. and its partners are 鈥渦nited in the belief that diplomacy continues to provide the most effective pathway to verifiably and permanently preventing Iran from obtaining a nuclear weapon.鈥

鈥淎nd,鈥 he said, 鈥渨e are united in the belief that negotiations should resume in Vienna as soon as possible and that they should resume precisely where they left off in June.鈥

The is charged with monitoring the 2015 accord, which was aimed at curbing Iran鈥檚 nuclear activity in exchange for the lifting of crippling sanctions. The U.S. pulled out of the accord under Donald Trump and re-imposed sanctions.

Since then Iran has stepped up nuclear activity and is now in violation of several aspects of the deal, known as the Joint Comprehensive Plan of Action or JCPOA.

Iran鈥檚 nuclear activity includes enriching uranium which Western nations fear could be used to build an atomic bomb. Tehran denies any such ambitions.

The U.S. and European partners are ready to return immediately to negotiations with Iran 鈥渋n order to swiftly conclude an agreement on Iran鈥檚 return to its commitments and the United States鈥 return to the JCPOA,鈥 Legendre said.

Iran鈥檚 new hardline government led by President Ebrahim Raisi, which took power in August, has hinted it will return to the nuclear talks in Vienna but has balked at setting a date.