Chief negotiators of Iran and the three European participants in the Vienna nuclear talks have returned to their capitals to hold consultations and update their respective governments.

European Union envoy Enrique Mora, who is the coordinator of the negotiations, told Iran International on Friday that he stays in Vienna where expert-level talks will continue over the weekend.

Russia’s top negotiator Mikhail Ulyanov said it is a two-day recess and doesn’t mean that the eighth round is over.

EU foreign policy chief Josep Borrell also 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," he said after an informal meeting of EU foreign ministers.

Borrell expressed hope to revive the agreement "in the coming weeks" so that it functions as it did before the American withdrawal.

Also on Friday, an unnamed source close to the talks told Reuters that “we are in the nitty gritty, it is the most tedious and demanding stage of negotiations as we’re increasingly dealing with the sequencing of nuclear and sanctions steps”, adding that the problem is not the issues but time “as we do not have all the time in the world”.