A US warship successfully shot down a target missile warhead over the Pacific in a test of a sea-based missile defense system, the US military said.

A Japanese destroyer performed surveillance and tracking exercises during the test, marking the first time any US ally has taken part in a US missile defense intercept test, the US Missile Defense Agency said.

The test came amid a confrontation with North Korea over its preparations to launch a long-range missile.

The sea-based system tested off Hawaii is designed to counter only short or medium range missiles, but the cruisers and destroyers that took part are capable of tracking long-range missiles as well.

The mock warhead was launched over the Pacific atop a medium range missile and destroyed in a direct hit six minutes later with an SM-3 missile fired by the Aegis cruiser USS Shiloh, the agency said.

"The missile successfully intercepted the target warhead outside the earths atmosphere more than 100 miles above the Pacific Ocean and 250 miles northwest of Kauai," the agency said in a statement.

"We are continuing to see great success with the very challenging technology of hit-to-kill, a technology that is used for all of our missile defense ground- and sea-based interceptor missiles," Lieutenant General Trey Obering, the agency chief, said in the statement...