European negotiators stressed Tuesday that talks to save the Iranian nuclear deal are "urgent", the day after discussions between world powers resumed in Vienna.

The nuclear talks had restarted on November 29, following a five-month hiatus to revive the 2015 nuclear deal, which would see the US lifting the sanctions it imposed on Tehran.

"This negotiation is urgent... We are clear that we are nearing the point where Iran's escalation of its nuclear program will have completely hollowed out the JCPOA," negotiators from Britain, France, and Germany (E3) claimed in a statement.

"That means we have weeks, not months, to conclude a deal before the JCPOA's core non-proliferation benefits are lost," they added.

Iran's uranium enrichment

On Saturday, Atomic Energy Organization of Iran director Mohammad Eslami confirmed Tehran had no plans to enrich uranium beyond 60 percent, even if the Vienna talks fail.

Eslami explained that the enrichment levels were related to the needs of the country, in remarks published by the Russian news agency RIA Novosti.

On the other hand, E3 negotiators said Tuesday that 60 percent enrichment was still "unprecedented for a state without nuclear weapons", while military-grade levels are around 90 percent.

"Its increasing 60 percent stockpile is bringing Iran significantly closer to having fissile material, which could be used for nuclear  weapons," they argued.

On good track

However, Iran's Foreign Minister Hossein Amir-Abdollahian was quoted by IRNA on Tuesday as saying that the negotiations were "on a good track."

"With the goodwill and seriousness from the other parties, we can consider (reaching) a quick agreement in the near future," he said.

For his part, Moscow's ambassador to the UN in Vienna, Mikhail Ulyanov, mentioned that the working group on nuclear issues held a "useful meeting" on Tuesday while lifting sanctions was also discussed informally.

"We observe indisputable progress," he wrote on Twitter.

Today in the course of #ViennaTalks on #JCPOA the working group on nuclear issues held a useful meeting. We observe indisputable progress. #Sanctions lifting is being actively discussed in informal settings. pic.twitter.com/GniRLV6CA7

— Mikhail Ulyanov (@Amb_Ulyanov) December 28, 2021

EU diplomat Enrique Mora, who is chairing the talks, said on Monday that all sides were showing "a clear will to work toward the successful end", but that "very difficult" negotiations lay ahead.