Iranian suicide drones supplied to Russia are inflicting losses on Ukrainian forces in the Kharkiv region, The Wall Street Journal reported Saturday.

Ukrainian military officers told the Journal that the drones, thought to be Shahed-136 UAVs operate in pairs, one targeting nearby radar as the second one locks on its target and slams into it. The drones have hit several Ukrainian armored vehicles and artillery batteries.

The United States warned in July that Russia was planning to acquire military drones from Iran, which has made significant progress in developing UAVs to compensate for its lack of an effective air force.

The Biden Administration has been negotiating with Iran since April 2021 to achieve to revive a nuclear deal that restricted Tehran’s uranium enrichment program. In exchange for lifting economic sanctions. The negotiations are currently stalled as Washington says Iran has made unacceptable demands.

Opponents of the deal argue that the US should not lift the sanctions and instead should intensify pressure as Iran’s economy faces serious challenges after four years US restrictions on its oil exports and international banking.

Iran is a close ally of Russia and the two countries closely collaborated in the Syrian war, where Moscow supplied air power and Tehran deployed thousands of militias against rebel forces.

Col. Rodion Kulagin of the Ukrainian army told the WSJ that “he hoped the U.S. and allies could provide Ukraine with more advanced antidrone technologies, or would step in to disrupt Iranian drone shipments to Russia.”