WASHINGTON (AP) — The White House voiced concern Tuesday that Iran may provide Russia with ballistic missiles for use in its war against Ukraine, a development that likely would be disastrous for the Ukrainian people, a U.S. national security official said.

National Security Council spokesperson John Kirby noted that Iran already has been providing Russia with unmanned aerial vehicles or drones, guided aerial bombs and artillery ammunition, and may be preparing “to go a step further in its support for Russia.”

Kirby highlighted a September meeting in which Iran hosted Russian Defense Minister Sergei Shoigu to show off a range of ballistic missile systems, sparking U.S. concern.

“We are therefore concerned that Iran is considering providing Russia with ballistic missiles now for use in Ukraine,” Kirby told reporters during a conference call. “In return for that support, Russia has been offering Tehran unprecedented defense cooperation, including on missiles, electronics and air defense.”

Kirby’s warning came as President Joe Biden’s request for more than $61 billion in emergency U.S. funding to continue to support Ukraine’s defense remained stalled in Congress. The additional aid for Ukraine is part of a larger $106 billion funding request from the Democratic president that also would support Israel, Taiwan and the U.S. operations on the border with Mexico.

A growing group of lawmakers in the Republican Party, which controls the House of Representatives, opposes sending more money to Ukraine.

Kirby and other top U.S. officials have been urging Congress to pass aid for Ukraine, saying existing funding is drying up.

He also noted Iran’s announcement earlier this year that it had finalized a deal to buy Su-35 fighter jets from Russia, and said Iran is looking to buy additional military equipment from Russia, including attack helicopters, radars and combat-trainer aircraft.

“In total, Iran is seeking billions of dollars worth of military equipment from Russia to strengthen its military capabilities,” Kirby said. “Russia has also been helping Iran develop and maintain its satellite collection capabilities and other space-based programs.”

He said the burgeoning military partnership between Iran and Russia is harmful to Ukraine, Iran’s neighbors in the Middle East and “quite frankly to the international community.”

At the direction of the Russian government, Kirby said the Wagner mercenary group was preparing to provide an air-defense capability to either Hezbollah or Iran. He said the U.S. would be watching to see whether that happens and was prepared to use “counterterrorism sanctions authority against Russian individuals or entities that might make these destabilizing transfers.” Russia has used Wagner in the past when it has wanted to be able to deny involvement, especially in foreign military operations.

The U.S. says the Kremlin’s reliance on Iran, as well as North Korea — countries largely isolated on the international stage for their nuclear programs and human rights records — shows desperation. That comes in the face of Ukrainian resistance and the success of the global coalition in disrupting Russian military supply chains and denying replacements for weapons lost on the battlefield. The White House has said Russia has turned to North Korea for artillery.

U.S. officials say Iran has also provided Russia with artillery and tank rounds for its invasion of Ukraine.

The U.S. and other countries have taken steps to thwart the potential supply, sale or transfer involving Iran and ballistic missile-related items, Kirby said. The U.S. has also issued guidance to private companies about Iranian missile procurement practices to make sure they aren’t inadvertently supporting Iran’s development efforts.

Last May, the White House said Russia was interested in buying additional advanced attack drones from Iran for use in the war against Ukraine after it used up most of the 400 drones it had previously purchased from Tehran.

A U.S. intelligence finding released in June asserted that Iran was providing Russia with materials to build a drone manufacturing plant east of Moscow as the Kremlin looks to lock in a steady supply of weaponry for the war.