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VANDENBERG AIR FORCE BASE, Calif. (Reuters) - The U.S. military has begun the first missile defense test involving a simulated attack by an intercontinental ballistic missile, firing off an interceptor from Vandenberg Air Force Base in California, a Reuters witness at the base said.

It could be several hours before the U.S. military discloses whether the Ground-based Midcourse Defense (GMD) interceptor struck its target. The test came as fears mount about North Korea’s advancing program to develop an ICBM capability.