Russia will send fighter jets and attack helicopters to Iran, state media says. The move could strengthen ties that already have the US worried.

• Russia is slated to send Iran advanced fighter jet and attack helicopters, reports say.
• Iranian state media says the agreement will strengthen the country's air force.

Russia has agreed to send advanced fighter jets and attack helicopters to Iran in a deal that would provide a significant boost to the country's air force, Iranian media reports.

The reported agreement comes as the US expresses greater concern over what it describes as increasing defense cooperation between Moscow and Tehran. A top White House official said last week that the "expanding military partnership" is "not good" for Ukraine or the Middle East region.

Plans have been finalized for Russia to deliver an unspecified number of Su-35 fighter jets, Mil Mi-28 attack helicopters, and Yakovlev Yak-130 jet trainers, the semi-official Tasnim News Agency reported on Tuesday, citing Iran's deputy defense minister. The report was then later confirmed on Wednesday by the official state-run Islamic Republic News Agency (IRNA).

The Kremlin has yet to publicly confirm the deal, which Tasnim said would be the first time that Tehran has purchased fighter aircraft since the 1990s.

Iran announced earlier this year that it had already finalized a deal to purchase the Su-35, a multi-role fighter that's been active in Ukraine, but Tehran was still looking to acquire additional military equipment — like attack helicopters and combat training aircraft — from Moscow.

White House National Security Council spokesperson John Kirby told reporters that this is part of the "increasing military cooperation" that's formulated between Russia and Iran as Moscow has become more isolated on the world stage over its unprovoked war in Ukraine.

This expanded defense partnership, he said, is "harmful" to Kyiv, Tehran's neighbors, and the international community.

Kirby said Iran has already provided Russia with artillery ammunition, guided aerial bombs, and drones — the most notorious of them being the Shahed loitering munitions, which have been used to terrorize Ukrainian cities and civilian infrastructure.

But the US is growing concerned that Tehran may go a step further than the support it has already provided and outfit the Russian war machine with ballistic missiles.

"In return for that support, Russia has been offering Tehran unprecedented defense cooperation, including on missiles, electronics, and air defense," Kirby said, adding that Iran is ultimately seeking billions of dollars worth of military equipment to strengthen its own capabilities.

"In response to Iran's support for Russia's war in Ukraine, we've already taken a range of steps, including implementing numerous US sanctions designations and working with partners like the European Union to expand the scope of their sanctions authorities and their designations," Kirby said.

IRNA noted that the Su-35s included in the reported agreement will provide a boost to Iran's military and "dispel rising suspicions" that Russia was taking advantage of Iran in their military cooperation. The agency also said the agreement is important to Moscow because it will "prove" it can still secure foreign military sales.

Prior to the invasion of Ukraine, Moscow was the world's second-largest arms exporter behind the US, according to a 2021 Congressional Research Service report. At the time, the Kremlin sold weapons to over 45 countries and since 2016 had accounted for 20% of global sales, with aircraft making up half of that number. But Russia's war in Ukraine has disrupted its foreign military sales, an important component of the country's defense apparatus.

The Institute for the Study of War, a Washington-based think tank, said the transfer of Russian aircraft could still take months to happen.

"Iranian leaders have repeatedly indicated since late 2022 that they would soon receive advanced aircraft from Russia without receiving anything yet," analysts wrote in a Tuesday assessment.

ISW's experts noted that Russia's military support to Iran comes as the two countries have "tried to coordinate politically vis-à-vis" the ongoing Israel-Hamas war. "Iranian and Russian officials have engaged one another repeatedly in recent weeks to discuss the war and cooperate in advocating for a ceasefire," they wrote.

Iran supports several militant groups across the Middle East, including Hamas in Gaza, Hezbollah in Lebanon, the Houthis in Yemen, and various proxies in Iraq and Syria. The US has repeatedly warned Tehran over the past few weeks to avoid allowing the conflict to escalate and spiral into a regional war, yet American forces in Iraq and Syria have still come under fire dozens of times.