A pilotless plane that the U.S. Army is testing in El Salvador by conducting reconnaissance missions for the Salvadoran government crashed yesterday, the U.S. Embassy in San Salvador and the Pentagon confirmed.

The plane, called a drone, had taken off from an airfield in San Lorenzo and crashed near San Carlos, 100 miles northeast of San Salvador.

The Pentagon said it did not know why the drone crashed but said it was not hit by hostile fire. It was the first known crash in El Salvador of the drone, a spokesman said.

The use of the drone in El Salvador is part of a stepped-up effort by the U.S. military to equip itself with new generations of pilotless planes that can fly over an enemy a battlefield in a war and send back images via television without risking lives of air crews.

Military officials said even Third World countries are arming themselves with such sophisticated antiaircraft weapons that U.S. warplanes cannot expect to fly against them without losses.

They cited the Dec. 4, 1983, Navy bombing raid in Lebanon where two bombers were lost and one pilot was killed. The raid was launched to retaliate for Syrian gunners in Lebanon firing at a Navy F14 reconnaissance plane.

Israel, rather than risk pilots and expensive planes, has developed a family of drones for reconnaissance and jamming antiaircraft defenses just before its manned bombers swoop in on their targets.

The U.S. Army, Navy, Air Force and Marine Corps all are trying to develop or buy better drones.

The Pentagon said a team of 20 Army and contractor personnel went to El Salvador in November with the Skyeye drone built by the Astronautics Division of Lear Siegler Inc.

The Skyeye is 12 feet long, has a wingspan of 17 1/2 feet and can stay aloft for up to eight hours with a light load.

An operator on the ground directs its movements with a joystick while sitting at a console displaying what the drone's cameras are seeing.

The Salvadoran government almost certainly has requested the U.S. operators of Skyeye to fly over areas suspected to have concentrations of rebel troops, although the Pentagon would not say what types of reconnaissance the drone was doing as part of its test program. If rebels were located by the drone providing what is called "real-time intelligence," government forces could move in on them.

U.S. Embassy spokesman Donald R. Hamilton in San Salvador confirmed the plane was on a U.S. intelligence-gathering mission in support of Salvadoran military operations, according to the Associated Press.

The Army is testing the Skyeye to see if it wants to buy it for its own forces, according to the Pentagon, but has not reached a decision.

The drone takes off under its own power and can land on the ground after its mission or, in an emergency, come down to earth by parachute.