"I deemed it necessary at this stage to consult the Russian authorities in order to continue the talks in a constructive atmosphere," Ali Bagheri, Tehran's chief nuclear negotiator, said on Tuesday according to Iranian state television's Iribnews website.

French Foreign Minister Jean-Yves Le Drian said "the talks should normally resume Thursday."

He added that he hoped they would be "positive".

The negotiations restarted on November 29 after a five-months hiatus, but diplomats agreed on Friday to pause the discussions for several days to allow consultations in capitals.

France said earlier Tuesday that proposals submitted by Iran at talks in the Austrian capital Vienna fell short of what was needed, and that time was running out.

The landmark 2015 accord aimed at putting curbs on Iran's nuclear programme to ensure it could not develop an atomic weapon, in exchange for sanctions relief for Tehran.

It was initially agreed between Iran and Britain, China, France, Germany, Russia and the United States.

But it began unravelling in 2018 when then US president Donald Trump pulled out and reimposed sanctions, prompting Iran to start exceeding limits on its nuclear programme the following year.

Iran has always insisted that its nuclear programme is peaceful.