Russian officials trained in Iran in recent weeks as part of an agreement on the transfer of drones between the two countries, the US has said, adding their drone deal is "potentially sanctionable."

US State Department deputy spokesperson Vedant Patel told reporters on Thursday that Russian officials had conducted training on drones in Iran "in the last several weeks." 

The United States would "vigorously enforce" its sanctions on both the Russian and Iranian weapons trade, he said. The transfers of drones between the two countries were "potentially sanctionable under numerous authorities," Patel said.

"We remain incredibly concerned about Iran's use and proliferation of UAVs [unmanned aerial vehicles]. They have been used to attack US forces, our partners in the region, and international shipping entities," the US official said.  

Tehran did not immediately comment on the US claim.  

US officials said last month that Washington had information that Iran was preparing to provide Russia with up to several hundred drones, including some that are weapons capable, and that Russian officials had visited Iran to inspect Predator UAVs.

The claim raised concerns that Iran, which has supplied drones to its allies in the Middle East, was now providing support to Russia for its attacks on Ukraine.

Iran's foreign minister at the time denied the claim, also over a phone call with his Ukrainian counterpart.

Last month US National Security Adviser Jake Sullivan said Iran will be providing "hundreds" of UAVs to Russia for its conflict in Ukraine.

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