Watch a Pentagon video of the missile test

Officials say an unarmed Minuteman missile fired from the Vandenburg Airbase in California across the Pacific on Saturday night was intercepted and destroyed by a "kill vehicle" launched from the Marshall Islands 6,880 km (4,300 miles) away.

The Minuteman target missile was launched from California

The intercept occurred high above the Ocean at a combined speed of almost 26,000 km/h.

"It looks like a great, big old bright flash," said spokeswoman Sheryl Irwin, who the test with military observers from the Pentagon.

"You saw it explode, and there was a loud roar - a very happy one - that went up from the room. It proves that this technology is working, and we can move forward with the programme."

'Hit to kill'

In a statement the National Missile Defence (NMD) Programme Office said the "hit to kill" test demonstrated that a warhead carrying a weapon of mass destruction aimed at the US could be "totally destroyed and neutralised."

The exercise was the first test of the Exoatmospheric Kill Vehicle, developed by US defence contractor Raytheon Corp.

The US military says the test proves the technology is working

In June the US military said it had completed the first successful test of the Theatre High Altitude Area Defence (Thaad) missile, designed to protect troops in the field by destroying medium-range enemy missiles well before they reach their target.

The new system tested on Saturday is designed to destroy long range intercontinental missiles launched by terrorists or countries the US considers to be so-called rogue states.

Last month a US intelligence report predicted that over the next 15 years the US is likely to face long range missile threats from Russia, China and North Korea, "probably" from Iran, and "possibly" from Iraq.

The system is not intended as a defence against a barrage of missiles launched by a major power.

Undermining deterrence

In June the US military conducted its first successful test of the Theatre High Altitude Area Defence (Thaad) missile designed to protect troops in the field by destroying medium-range enemy missiles in flight before they reach their target.

US intelligence reports say there is a growing threat from foreign missiles

Critics of the new system say it amounts to a preparation for war and the Russian government has expressed concerns that a fully operational US anti-missile defence system could undermine nuclear deterrence.

Moscow has raised objections to US moves to make amendments to the 1972 Anti-Ballistic Missile treaty that would allow the American military to develop and deploy such a system.

Saturday's test costing about $100m was the first of three scheduled before the Pentagon decides next June whether or not to continue with the project.