The head of the Missile Defense Agency called it "the largest, most complex test we have ever done" and labeled it a success

Dec. 5, 2008: A Ground-Based Interceptor is shown shortly after liftoff from Vandenberg Air Force Base, Calif. The Pentagon's Missile Defense Agency used the interceptor missile to knock down a missile meant to simulate the speed and trajectory of a North Korean attack

WASHINGTON -- The Defense Department said Friday it shot down a missile in a simulated attack designed to test a proposed shield against strikes by long-range ballistic missiles from nations such as North Korea.

The Pentagon's Missile Defense Agency used an interceptor missile launched from Vandenberg Air Force Base in California to knock down a missile meant to simulate the speed and trajectory of a North Korean attack. It struck the target missile around 3:30 p.m., shortly after the target was launched from a location in Alaska.

The military has conducted a series of tests in the past several years of the different components of the defensive shield, which is slated to include Patriot air defense batteries, anti-ballistic missiles launched from Navy ships and lasers mounted in planes designed to shoot down incoming missiles.

Friday's test, which cost between $120 million to $150 million, incorporated many of the network's multiple systems. For example, the Navy tracked the target from one of its ballistic missile ships but did not fire.

"It was the largest, most complex test we have ever done," said Lt. Gen. Patrick O'Reilly, head of the Missile Defense Agency.

O'Reilly characterized the test as a success, but the target did not release planned countermeasures designed to try to confuse the interceptor missile. O'Reilly did not say what those countermeasures were, but they often include decoys or chaff to throw off shoot-down attempts.

Roughly $10 billion is spent per year on the program, which is run by defense contractor Boeing Co. but includes work by most of the nation's largest weapons makers. It is spread across three branches of the military and is composed of missiles, radar and satellites designed to intercept missiles during different stages of flight.

The military argues the network is needed to protect the United States and its allies against growing threats from nations such as Iran and North Korea, both of which have tested long-range missiles. But President-elect Barack Obama expressed skepticism about the capabilities of the system during his campaign, leading to speculation he may reduce the program's scope. Russia has strongly objected to plans to install missile interceptors in Eastern Europe.

Brian Green, a deputy assistant secretary of defense, said the successful test should help bolster the missile defense program. "Successful tests always help reinforce confidence in the system," he said.

Friday's test covered ground-based missile interceptors located at military bases located in California and Alaska meant to shoot down incoming missiles mid-flight. A ground-based missile successfully shot down a target during a similar test in 2007, but the Pentagon was forced to scale back plans for a test last summer because of a technical glitch.