Gavin Williamson said the specially-adapted drones could be in operation by the end of 2019.
He also warned in a speech that the UK needs a bolder and stronger armed forces prepared to use "hard power".
Labour has said the military's role on the international stage had been "completely undermined" by Tory cuts.
South China Sea
Speaking at the Royal United Services Institute, Mr Williamson said Britain must stand up to those who "flout international law".