The US military says that when it destroyed an Iranian drone last week over the Strait of Hormuz, it also took aim at a second drone.
Iran denies it lost any drones.
US Central Command said that one Iranian drone crashed into the sea after the USS Boxer took what Central Command called "defensive action" against the drone last Thursday. CENTCOM said the Boxer also "engaged" a second Iranian drone at the same time, but could not confirm it was destroyed.
Officials have said the Boxer used an electronic jamming device on the ship to attack the drones, rather than fire missiles at it.
US officials said the drones acted aggressively toward the Boxer in international waters and were part of a pattern of efforts by Iran to disrupt navigation.