Russian Foreign Ministers Sergei Lavrov and Iranian Hossein Amir Abdollahian expressed a unified position on the formula for returning to the nuclear agreement, which major powers and Tehran are preparing to resume negotiations to revive it after several stalled rounds.

The Russian Foreign Ministry said - in a statement - that the Russian and Iranian ministers called in a telephone conversation between them today, Saturday, for the need to return to the nuclear agreement in its original form.

In the same call, the Iranian foreign minister stressed that "Tehran is serious about negotiations and the implementation of our nuclear commitments, and the other parties should implement their commitments."

And the Iranian Atomic Energy Organization announced on Friday that the country continues to expand its nuclear program, although international negotiations are scheduled for the end of November in Vienna.

"We have so far produced 25 kilograms of 60% enriched uranium, which no country can produce except for countries that have nuclear weapons," official Iranian media quoted a spokesman for the Atomic Energy Organization of Iran, Behrouz Kamalvandi, as saying.

6 rounds of negotiations in Vienna failed to reach a unified formula on reviving the nuclear agreement between Tehran and major powers (Reuters)

It is scheduled to resume negotiations to revive the 2015 nuclear agreement with world powers on November 29, in Vienna.

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Western powers say the chances of salvaging the agreement are diminishing in light of Iran's acceleration of uranium enrichment close to the level required to make weapons, considering this a violation of the restrictions stipulated in the agreement.

Tehran has previously denied seeking nuclear weapons, saying it is only enriching uranium for civilian energy uses, and said its violations could be reversed if the United States lifted sanctions and rejoined the deal.

But it returned and stated last June that it had produced 6.5 kilograms of 60% enriched uranium.

And last April, the International Atomic Energy Agency of the United Nations said that Tehran had started the process of enriching uranium to a purity of 60% in an above-ground nuclear facility in Natanz, confirming previous statements by Iranian officials.

The nuclear agreement limits the degree of purity at which Tehran can enrich uranium to no more than 3.67%, which is the appropriate level for most civilian nuclear energy uses.

This percentage is well below the 20% achieved by Iran before the 2015 agreement and well below the 90% suitable for making a nuclear weapon.

The administration of US President Joe Biden says that it wants to return to the agreement that the administration of its predecessor, Donald Trump, withdrew from, but it does not agree with Tehran on the steps that should be taken and the timing of these steps.

The main outstanding issues now revolve around the nuclear limits that Tehran will accept, and the sanctions that Washington will lift.

Western officials and analysts believe that Tehran's increase in the level of uranium enrichment with its deliberation in returning to the talks - which was postponed last June when a new president was elected - aims to strengthen its positions to extract more concessions when negotiations resume.