Iran also initially denied it had supplied Russia with combat and reconnaissance drones—most notably the Shahed-136 "kamikaze" UAV (unmanned aerial vehicle)—but later admitted it had sent a small number to Moscow before the full-scale invasion began on February 24.There has also been speculation that Moscow will reward Tehran for its backing by protecting Iran from international action over its revitalized nuclear program and sending Iran new weapons.The deputy secretary of state said the U.S. was firmly committed to backing Kyiv against Russia's ongoing aggression, regardless of threats of escalation from President Vladimir Putin or rumors that the dictator would order further military mobilization.Ukraine has warned that another wave of mobilization might see 500,000 Russians conscripted.The Kremlin gathered 300,000 new recruits in the first wave of partial mobilization announced in September."