A test of a powerful missile-intercepting laser, scheduled for Sunday morning, was postponed for the fourth time due to technical problems, Pentagon's Missile Defense Agency said on its website.

The laser, housed aboard a modified Boeing 747-400 Freighter, was to intercept a simulated short-range ballistic missile during Sunday's tests, to be held off California's coast. The previous tests were scheduled during the past three weeks.

"Trouble shooting indicates that a hot bypass valve on the aircraft is in an abnormal condition thus not allowing for proper component cooling," the agency said in a statement. "The team is evaluating the potential causes."

"A new date for the experiment will be set for the upcoming week," the statement reads.

The Airborne Laser Test Bed (ALTB) uses two solid state lasers and a megawatt-class Chemical Oxygen Iodine Laser (COIL) against ballistic missiles. It uses six infrared sensors to detect the exhaust plume of a boosting missile.

As soon as a target is detected, a kilowatt-class solid state laser, the Track Illuminator, tracks the missile and determines a precise aim point.

The Beacon Illuminator, a second kilowatt-class solid state laser, then measures disturbances in the atmosphere, which are corrected by the adaptive optics system to accurately point and focus the high energy laser at its intended target.

Using a very large telescope located in the nose turret, the beam control/fire control system focuses the COIL beam onto a pressurized area of the boosting missile and holds it there until the concentrated energy compromises the structural integrity of the target, causing it to fail.

MOSCOW, August 23 (RIA Novosti)