WASHINGTON (CNN) -- A missile shield test was a "smashing success," Pentagon officials said Friday, despite the failure of the test to put to rest concerns that the interceptor might not be able to differentiate between real missiles and decoys.

Eight of the United States' 13 missile defense tests have been deemed a success.

The ground-based interceptor missile, launched from Vandenberg Air Force Base in California, destroyed a long-range ballistic missile launched from Kodiak, Alaska, the Defense Department's Missile Defense Agency said.

But one key aspect of the test -- to see whether the system could tell the difference between a missile and a decoy aimed at confounding its "seek" systems -- failed because the decoy did not deploy.

Officials told CNN on Thursday that Friday's test would be the most realistic of 13 missile shield system tests conducted to date. Eight of the 13 tests have now been deemed a success by the Pentagon. Watch a Pentagon spokesman explain the Friday's problem »

This was the first test in which a crew at an alternate fire control center in Alaska remotely launched the interceptor missile from California.

The "initial indications," according to the Defense Department, are that all components of Friday's test performed as designed.

Critics have long complained that the tests are not realistic because they don't involve balloons or other simple decoys that, they argue, could easily fool the interceptor. Watch a report on the defense system »

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In Friday's test, however, the target was a mock warhead and was supposed to be accompanied by "countermeasures similar to what Iran or North Korea could deploy," according to a missile defense agency official. The intention was for the interceptor's kill vehicle to distinguish the target from the decoys.

But the decoy that was supposed to deploy to test the system did not. The Pentagon blamed a 40-year-old target system.

"Countermeasures are very difficult to deploy. We have had trouble deploying them in the past," said Lt. Gen. Patrick J. O'Reilly, director for the Missile Defense Agency. But O'Reilly said that the interceptor did differentiate between the actual missile target and the upper stage of the missile it had detached from.

The test, which had been delayed several times, comes at a crucial time for the $100 billion system, as President-elect Barack Obama is about to take office.

Early in his campaign, Obama pledged to "cut investments in unproven missile defense systems." But he later said he would support missile defense systems if they work.

"The biggest threat to the United States is a terrorist getting their hands on nuclear weapons," Obama said in the September 26 presidential debate.

"And we are spending billions of dollars on missile defense. And I actually believe that we need missile defense, because of Iran and North Korea and the potential for them to obtain or to launch nuclear weapons."

Friday's test also showed the Pentagon that multiple sensor systems were able to network together and hone in on a single object, O'Reilly said.

"All those sensors working together, at any one time the system knew which sensor was reporting what and tracking it and gave the war fighter one presentation of a target," O'Reilly said soon after the test was finished. "That was one tremendous accomplishment for us."

Last month, the outgoing head of the Missile Defense Agency said that not only are U.S. missile defenses workable, they are up and running.

"Our testing has shown not only can we hit a bullet with a bullet, we can hit a spot on the bullet with a bullet. The technology has caught up," Lt. Gen. Trey Obering said.

CNN's Jamie McIntyre and Adam Levine contributed to this report

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