In the letter, the chairman of the Ukrainian parliament, Ruslan Stefanchuk, calls on the U.S. to provide Ukraine with highly mobile air defense systems known as C-RAMs, saying they would help protect "important objects, especially crucial power plants."A senior Ukrainian politician told ABC News that the Ukrainian government has also made an official request to the Biden administration for the C-RAMs systems.However, Pentagon spokesperson Lt. Col. Garron Garn told ABC News this week that U.S. support "focuses on equipment that is relevant for the current fight."The White House National Security Council spokesperson, John Kirby, also said at the time that a "relatively small number" of Iranian personnel had been on the ground in Crimea to assist the Russians in how to operate the drones.However, Ukrainian officials said the drones are able to change trajectory mid-flight, making it harder for the military to position assets that could shoot them down."