US successfully shoots down simulated intercontinental ballistic missile in unprecedented test launch

The US military says it has intercepted a mock-up of an intercontinental ballistic missile in a first-of-its-kind test that comes amid concerns over North Korea's weapons program.

A ground-based interceptor launched from Vandenberg Air Force Base in California "successfully intercepted an intercontinental ballistic missile target" fired from the Reagan Test Site in the Marshall Islands, the military said in a statement.

"This system is vitally important to the defense of our homeland, and this test demonstrates that we have a capable, credible deterrent against a very real threat," Vice Admiral Jim Syring, director of the US Missile Defense Agency, said.

The test comes a day after North Korea test-fired yet another ballistic missile, the latest in a series of launches that have ratcheted up tensions over its quest to develop weapons capable of hitting the US.

Pentagon spokesman Navy Captain Jeff Davies said today’s test was not timed specifically to the current tensions in North Korea but said that "in a broad sense, North Korea is one of reasons why we have this capability".

"North Korea has expanded the size and the sophistication of its ballistic missile forces," Mr Davis said.

"They continue to conduct test launches, as we saw this weekend, while also using dangerous rhetoric that suggests they would strike the United States homeland."

Mr Davis also pointed to Iran's increasing missile capabilities as threatening US strategic interests in the Middle East.

The exercise will check the performance of the Ground-based Midcourse Defense (GMD) system, which has had a checkered record in previous tests.

Though it succeeded in the last test in 2014, it failed during the three prior attempts against slower-moving, non-ICBM missiles.

The technology behind the GMD is extremely complex, and the system uses globally deployed sensors to detect and track ballistic missile threats.

In a move that the Pentagon says is akin to hitting a bullet with another bullet - though at far higher speeds - the missile launches into space, then deploys an "Exo-atmospheric Kill Vehicle" that uses kinetic energy to destroy the incoming target.

The successful test is proof that America has an effective ground-based defense against ICBMs, albeit on a limited scale.

The system will comprise 44 interceptors by the end of the year, so it could thwart an attack from a rogue state or a volley of rockets.

But the interceptors, based in California and Alaska, would be overwhelmed by a full-scale attack from countries like Russia or China, which could fire dozens of missiles at a time.