The Pentagon says its forces successfully conducted a ballistic missile defense test over the Pacific on Friday, further demonstrating the capabilities of the ground-based system the United States wants to deploy to Poland and the Czech Republic. But a key part of the test did not go as planned.

Ground-based Interceptor is shown shortly after liftoff from Vandenberg Air Force Base, Calif., 05 Dec 2008

Officials say a missile launched from California hit a target that had been launched from Alaska 29 minutes earlier. The Pentagon says this test demonstrated the ability of four separate radar systems to work together and direct a kill vehicle into the path of an incoming missile 1,300 kilometers away, and 200 kilometers high, traveling at 10 kilometers per second.

But the target missile, a 40-year-old Cold War relic, failed to deploy the decoys that were designed to stress the intercept system, and determine whether it can differentiate between the real warhead and the decoy. Still, the new head of the Defense Department's Missile Defense Agency, Lieutenant General Patrick O'Reilly, says the test was valuable. "Overall, I'm extremely pleased because the key to our protection, and the effectiveness of the system, is to be able to have all of these sensors simultaneously tracking, and the system knows exactly that it's not multiple objects, it's one object up there, or cluster, exactly what it is. The kill vehicle was sent to a very accurate spot in space and that does give us great confidence."

General O'Reilly says future tests will use a new target missile that should deploy the decoys, known as countermeasures. But he says the missiles used by most countries that could potentially threaten the United States or its allies do not yet have countermeasures, although those countries, including North Korea and Iran, are working to improve their systems.

And although this test was conducted over the Pacific Ocean, he says it had "operational realism" and its "similar geometry" to a missile launched from North Korea toward the United States. He also says the same scenario would apply anywhere in the world to a missile launched with a range of about three thousand kilometers. That is just about the distance between, for instance, Tehran and Warsaw.

The general says the system tested Friday is very similar to the one planned for deployment in Poland and the Czech Republic. Russia strongly objects to the plan to put a radar system in Poland and an anti-missile launch site in the Czech Republic. But U.S., Czech and Polish officials say the system is purely defensive, and focused on the threat from Iran, and poses no threat to Russia.

Critics say the $100-billion U.S. missile defense system is too expensive and has not been proven to be effective. But officials say this was the eighth successful intercept by the ground-based part of the system, of 13 tests conducted since 1999. Officials say the missile shield is partly operational as testing continues.