The White House disclosure last week that Russia is seeking hundreds of armed and unarmed surveillance drones from Iran to use in the war in Ukraine reflects Moscow’s need to both fill a critical battlefield gap and find a long-term supplier of a crucial combat technology, U.S. intelligence, military and independent analysts say.

Jake Sullivan, U.S. President Joe Biden’s national security adviser, offered few details about the intelligence assessment he revealed to reporters July 11, including whether the shipments had started. But other American officials said Iran was preparing to provide as many as 300 remotely piloted aircraft and would start training Russian troops on how to use them as early as this month.

Russia has exhausted most of its precision-guided weapons as well as many of the drones it has used to help long-range artillery strike targets in its monthslong bombardment of Ukraine. Meanwhile, the first batches of U.S. truck-mounted, multiple-rocket launchers have destroyed more than two dozen Russian ammunition depots, air defense sites and command posts, according to two American officials, making Moscow’s need to counter the new, advanced Western arms more urgent.