The Pentagon has announced the failure of its latest test of an interceptor missile - part of President George W Bush's missile defence programme.

The defensive missile - supposed to hit an oncoming long-range enemy missile - did not separate from its booster rocket, the Pentagon said in a statement.

We do not have an intercept Rick Lehner, Air Force Lieutenant

Air Force Lieutenant Colonel Rick Lehner said it was "frustrating and disappointing" that the test had failed as a result of a glitch that had little to do with advanced missile technology.

This was the third missile test to fail of a total of eight carried out so far.

In June, the United States withdrew from the 1972 Anti-Ballistic Missile Treaty it signed with the former Soviet Union, seeing it as constraining its ability to test new anti-missile defences.

Despite international criticism, Washington has insisted on developing the programme to defend against incoming missiles from what it calls "rogue states".

Second case

In Wednesday's test, a Minuteman II intercontinental ballistic missile carrying the dummy enemy missile was launched from Vandenberg Air Force Base in California at 0826 GMT, the statement said.

About 20 minutes later, the rocket carrying the defensive missile was launched about 7,725 kilometres (4,800 miles) away from Kwajalein Atoll in the Republic of the Marshall Islands.

But the $100m missile failed to disengage from the booster. A similar fault occurred in July 2000.

The missile shield is in the planning stage

"We do not have an intercept," said Colonel Lehner of the Pentagon's Missile Defense Agency.

The Pentagon statement said two new rocket designs were being developed and would be tested next year.

In June, the US started work on the construction of a test site for the missile defence system.

A set of silos is being built in Alaska to house interceptors capable of destroying missiles fired by "rogue states" like North Korea, Iraq or Iran.

The silos, initially classified as test facilities, are expected to be fully operational by 2007.

There has been considerable scepticism that the eventual goal, of a comprehensive shield capable of protecting the US from any missile attack, will ever be achievable.