TWENTYNINE PALMS, Calif. (AP) _ ''Gallant Eagle '86,'' a 10-day exercise testing U.S. forces under desert warfare conditions, wound down Saturday with a live-ammunition drill in the Mojave Desert, a spokesman said.

''There's a live-fire exercise going on right now in Twentynine Palms, and with the end of that, the exercise will stand down,'' said Air Force Maj. John Meyer, spokesman for the joint-service command post at March Air Force Base.

Although it would take several days to analyze the performance of thousands of Army, Navy, Marine and Air Force units, ''everyone generally feels happy and satisfied,'' Meyer said.

An Ohio Army private was killed and several others were injured, including a Georgia soldier whose right hand was nearly severed, during the exercise, but the total number of injuries during the exercise had not been tallied, he said.

Three men were killed in a helicopter crash July 10 during pre-exercise preparations, Meyer said.

The exercise, centered at the Marine Corps Air Ground Combat Center here, 130 miles east of Los Angeles, was to test military personnel in a desert environment should they be called to action in the Middle East.

It was also a test to find out whether the services can be coordinated in one effort, said Marine Col. Bill Wydo.

During the maneuvers across hundreds of miles of California wasteland, troops fired live ammunition, coped with searing desert heat and learned how to fight by day and night.

The Air Force flew hundreds of missions from bases nationwide, and the Navy used container ships similar to those used by the British during the Falkland Islands war to support the massive exercise.

One of the Gallant Eagle highlights was Friday's successful night airborne assault by 742 Army paratroopers.

Safety has been stressed since the 1982 Gallant Eagle maneuver, when six paratroopers were killed and 150 were injured during a tactical drop in high winds.