UPDATE 1 — Trump to convert triumphal arch into military complex

(Adds background from paragraph 2 onwards) Sept 20 (Reuters) — US President Donald Trump said on Sunday he had agreed to a request by the military to convert his proposed triumphal arch near Arlington National Cemetery in Washington into a complex to house and deploy drones and sniper ammunition. The president cited national security concerns for the move, without mentioning any specific threats. The Federal Aviation Administration said last week that the 250-foot (76-meter) arch would not pose a hazard to aircraft but would be required to have an "eternal flame" on top, clearing an aviation hurdle for the arch, which Trump proposed to mark the nation's 250th anniversary. Aviation experts have raised safety concerns given its proximity to Reagan Washington National Airport while veterans have sued to block the arch, arguing it would destroy the historic sightline between the Lincoln Memorial and Arlington National Cemetery. The project is part of the president's broader drive to reshape Washington's monumental landscape, including a new White House ballroom, renovation of the Lincoln Memorial Reflecting Pool and redevelopment of a golf course in East Potomac Park. (Reporting by Anu