The intelligence suggests that Iran has been asking Russia for help acquiring additional nuclear materials and with nuclear fuel fabrication, CNN quoted sources briefed on the matter.

The fuel could help Iran power its nuclear reactors and could potentially further shorten Iran’s so-called “breakout time” to create a nuclear weapon.

While experts emphasized that the nuclear proliferation risk varies depending on which reactor the fuel is used for, they emphasized that it is also not clear whether Russia has agreed to help, given that the Kremlin has long been outwardly opposed to Iran obtaining a nuclear weapon.

US President Joe Biden’s administration is watching any new areas of cooperation between Iran and Russia with concern.

Any covert Russian assistance to Iran that could boost Iranian efforts to produce a nuclear weapon would also mark a significant shift in Russian policy, given Russia’s membership of the P5+1 group of countries that have been part of the negotiations to stymie Iran’s nuclear program.

The P5+1 group refers to the UN Security Council's five permanent members, namely Russia, China, France, the United States, and the United Kingdom, plus Germany, that were part of the 2015 Joint Comprehensive Plan of Action (JCPOA) with Iran.

“As we have said, the JCPOA is not on the agenda,” National Security Council spokesperson Adrienne Watson told CNN, referring to the formal name for the Iran nuclear deal.

“We have been working with partners to expose the growing ties between Iran and Russia – and hold them accountable. We will be firm in countering any cooperation that would be counter to our non-proliferation goals.”

Iran’s overtures to Russia appear at least partly motivated by a belief among senior Iranian officials that a new nuclear deal either won’t be revived or, if it is, won’t last.

Sources briefed on the intelligence said Iran’s fear was that a future administration might pull out of a deal, as the Trump administration did in 2018, so it sought a side deal with Russia that would allow it to reconstitute its nuclear program quickly if necessary.

Asked whether the growing Iran-Russia partnership was a factor in the nuclear deal talks getting derailed, a senior administration official said, “Obviously, side deals between Russia that fundamentally undermined the structure of the 2015 agreement would be a serious concern and further reduce the possibility of a return to the agreement.”

James Acton, co-director of the Nuclear Policy Program at the Carnegie Endowment for International Peace, said he does not believe Iran necessarily needs the help.

“But they (Iranians) do have clear incentives to ask for help, particularly on the fuel side,” Acton said.

“Three to four years ago, when US-Russia relations were bad, but not catastrophic, I would be pretty skeptical that Russia would provide Iran with help,” Acton added.

“But under today’s conditions, under which US-Russia relations are extremely bad and Russian-Iranian relations are getting better, I think the equation looks quite different for Russia,” he concluded.