Russia is looking to purchase more advanced drones from Iran, while at the same time Iran is looking to buy “billions of dollars of military equipment” from Russia, said White House National Security Council spokesman John Kirby.

The United States is seeing more indications that Russia and Iran are expanding a defence partnership in a way that will help Moscow prolong its war in Ukraine, the White House said recently. John Kirby explained that Iran is looking for Russian equipment such as aircraft and other military hardware that would increase the security threat to Iran’s neighbours.

“This is about a burgeoning defense relationship…that goes both ways,” said Kirby. He added that Washington is exploring more sanctions on Iran.

“We are using the tools at our disposal to expose and disrupt these activities, and we are prepared to do more,” Kirby told reporters, adding that drones are the primary military help Iran is providing to Russia, which is seeking to acquire advanced level types.

Iran announced two months ago that it reached a deal to buy advanced Su-35 fighter planes from Russia. Iranian state media said Iran had asked a number of countries to explore the possibility of selling it fighter jets, and Russia had given a positive response to the request. Details of the deal were not disclosed.

Iran has acknowledged sending drones to Russia but said they were sent before Russia launched its full-scale invasion of Ukraine last year. Moscow denies that its forces use Iranian-built drones in Ukraine, although many have been shot down and recovered there.

Iran’s air force has only a few dozen strike aircraft, including Russian jets and aging U.S. models acquired before the Iranian revolution of 1979.