An interceptor missile failed to launch early Wednesday in what was to have been the first full flight test of the U.S. national missile defense system (search) in nearly two years.

The Missile Defense Agency (search) has attempted to conduct the test several times this month, but scrubbed each one for a variety of reasons, including various weather problems and a malfunction on a recovery vessel not directly related to the equipment being tested.

A target missile carrying a mock warhead was successfully launched as scheduled from Kodiak, Alaska, at 12:45 a.m. EST, in the first launch of a target missile from Kodiak in support of a full flight test of the system.

However, the agency said the ground-based interceptor "experienced an anomaly shortly before it was to be launched" from the Ronald Reagan Test Site (search) at Kwajalein Atoll in the central Pacific Ocean 16 minutes after the target missile left Alaska.

An announcement said the interceptor experienced an automatic shutdown "due to an unknown anomaly."

The agency gave no other details and said program officials will review pre-launch data to determine the cause for the shutdown.

The military is in final preparations to activate missile defenses designed to protect against an intercontinental ballistic missile attack from North Korea or elsewhere in eastern Asia.

Wednesday's test was to have been the first in which the interceptor used the same booster rocket that the operational system would use.

In earlier testing of tracking and targeting systems, which critics derided as highly scripted, missile interceptors went five-for-eight in hitting target missiles.