A Lockheed Martin Corp built Aegis missile defence system on Thursday shot down a dummy warhead over Hawaiian waters in the sixth such successful, ship-based, intercept test in seven tries, the Pentagon's Missile Defence Agency announced.
The test off Kauai was the first of its kind involving a "separating" target - a warhead that had already parted its booster rocket, the agency said.
"Hitting something like this in space is trickier than when it's still attached to its large rocker motor," said Richard Lehner, a spokesman.
Previous targets were representative of single-stage "SCUD"-type ballistic missiles. The sea-based tests, begun in 2002, involve obliterating the target by colliding with it in space.
Bethesda-based Lockheed, the Pentagon's largest supplier, said the Aegis weapons system and space sensors had confirmed a direct hit.
The Aegis ballistic missile defence accounts for much of the sea-based leg of a broader bulwark against a limited missile attack of the type that US officials fear could be launched by North Korea.
All told, the United States is now spending about $9 billion a year on missile defence, the most expensive single weapons programme.
The maritime component is designed to knock out short- to intermediate-range ballistic missiles. A ground-based leg, run by Boeing Co to thwart threats in the middle of their flight paths, has shot down five targets in 10 tries.