Pentagon officials said the failure occurred in the interceptor's boost phase when the "kill vehicle," which is designed to seek out and destroy the incoming warhead in space, failed to separate from the booster rocket's second stage.

"We did not intercept the warhead that we expected to have tonight," said Lieutenant General Ronald Kadish, director of the Pentagon's Ballistic Missile Defense Organization. "We're disappointed with that."

It was a major setback for a project that is designed to protect the United States against a limited attack by ballistic missiles but which has aroused a storm of criticism from experts who said it could not work.

President Bill Clinton is to decide before the end of the year whether to go ahead with construction of the initial phase of the system so that it will be ready by 2005. US intelligence officials believe North Korea will have a missile capable of reaching the United States by then.

Pentagon officials would not say whether the failure doomed the chances of declaring the system technologically fit for deployment by 2005.

Of two previous attempts, only one has succeeded. That one successful intercept was conducted last October under less demanding conditions.

"If you had the time, you wouldn't like to make a go-ahead decision of any sort on the basis of what we've seen so far, and there was just these three flights," said Jacques Gansler, under secretary of defense for acquisition and technology.

But he said the president will have to decide whether there is enough information to order construction of a radar site on Shemya island in Alaska, which officials say must begin early next year if they are to make the 2005 deadline.

Saturday's test was likely to be the last one before the president makes his decision, though Gansler said another test was scheduled for October or November.

A target missile was launched into space 12:19 a.m. (0419 GMT) from Vandenberg Air Force Base in California, armed with a dummy warhead and a balloon decoy.

The interceptor missile was launched on cue 21 minutes later from Kwajalein atoll in the Marshall Islands, officials said.

A network of early warning satellites, ground radars and a high frequency targeting radar were supposed to guide it to a collision at closing speeds of 24,000 kilometers (15,000 miles) per hour.

But failure struck as the interceptor missile was boosting into space, they said.

A computerized command that was supposed to separate the so-called "kill vehicle" from the second stage of the booster never came, Kadish said.

"It was looking for a second stage separation signal. It did not get that," Kadish said.

As a result, the kill vehicle was never released to seek out and destroy the incoming warhead, as it is designed to do, Kadish said.

"What it tells me is that we have more engineering work to do," he said.

The balloon decoy in the target missile also failed to inflate, Kadish said, adding it would be several days before officials could piece together what went wrong.

The 100-million-dollar test had attracted criticism and protests even before its launch.

Seven Greenpeace activists were apprehended near the launch pad at Vandenberg Air Force Base, and two others were detained on Kwajalein atoll, the environmental group said in a statement. Officials at Vandenberg declined to comment.

On Friday, Professors Theodore Postol and George Lewis at the Massachusetts Institute of Technology (MIT), told the New York Times that "bagging the sort of precooked and strapped-down chicken of a target that is being used" would not prove the system's effectiveness.

Other critics questioned the Pentagon's assessment of the missile threat posed by adversaries like North Korea and Iran, and warn that fielding even a limited missile defense system could unravel international arms control regimes and ignite a nuclear arms race.

The US intelligence community is currently updating its assessment of the threat, officials have said.

Plans call for deployment of a targeting radar and 20 interceptors in Alaska by 2005. The system would be expanded to 100 missiles by 2007.

Russia and China vehemently oppose deployment of the system, which would violate the 1972 Anti-Ballistic Missile Treaty.

Russia "hopes that the unsuccessful anti-missile test means the national missile defence system is not deployed," the ITAR-TASS new agency quoted the unnamed official as saying.

The defence ministry's General Leonid Ivashov said the botched test "shows once again that the idea of building a national missile defence system is suspect from the military-political point of view as well as the point of view of technical possibilities," Interfax reported.

Clinton is due to take a final decision on deployment in the light of a third test on the putative system, which failed Saturday.

The scheme has been dubbed "son of Star Wars" by critics, a reference to US plans under the then president Ronald Reagan to erect a space-based system to defend against rocket attack.

Deployment would breach the landmark 1972 Anti-Ballistic Missile Treaty which has been the cornerstone of arms control accords between Russia and the United States for almost 30 years.

Ivashov said Russia "will always have the means to overcome any American ABM system," adding the only question was whether it was worthwhile to spend money on a system which could be "destroyed by political means."

Missile defence experts on both sides acknowledged it was impossible to build a perfect defence system said Ivashov, a hardliner in charge of international relations.

Russian President Vladimir Putin has vowed to tear up all agreements if the Clinton administration moves to deploy the system without first reaching an agreement with Moscow on revising ABM.

Contacted by AFP, the Russian foreign ministry had no immediate official comment on the failed US test.

Washington has argued it needs a national missile defence system to protect itself from the threat posed by so-called "rogue" nuclear threshold states like North Korea and Iraq.

But Moscow says the threat is exaggerated and has refused to amend ABM.

Hijacking Satellites Via The Net
London - July 6, 2000 - In a week when NASA revealed that a computer hacker interrupted communications on a space shuttle mission in 1997, a new space research project has been launched which could give hackers the ultimate kick: control of a spacecraft.