Iran has reached a deal to buy advanced Su-35 fighter planes from Russia, Iranian state media said on Saturday, expanding a relationship that has seen Iranian-built drones used in Russia's war on Ukraine.

"The Sukhoi-35 fighter planes are technically acceptable to Iran, and Iran has finalized a contract for their purchase," the broadcaster IRIB quoted Iran's mission to the United Nations as saying in New York.

The report did not carry any Russian confirmation of the deal, details of which were not disclosed. The mission said Iran had also inquired about buying military aircraft from several other, unnamed countries, IRIB reported.

Russian President Vladimir Putin met Iranian Supreme Leader Ayatollah Ali Khamenei in Tehran last July, stressing closer ties in the face of Western pressure over the war in Ukraine.

Iran has acknowledged sending drones to Russia but says they were sent before Moscow's 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: Russian jets, as well as aging U.S. models acquired before the Iranian revolution of 1979.

In 2018, Iran said it had started production of the locally designed Kowsar fighter for use in its air force. Some military experts believe the jet is a carbon copy of an F-5 first produced in the United States in the 1960s.