The U.S. military postponed a missile defense test yesterday off Hawai'i after a small craft ventured into a no-entry zone blocked off for the drill.

The military rescheduled the test for today because the vessel was unable to get out of the restricted area in time, said spokesman Chris Taylor.

Taylor did not specify what kind of craft entered the zone, but "small craft" is a technical classification that usually refers to sailboats, fishing boats and vessels of similar size.

The military's latest test for its sea-based missile defense program comes as international tensions brew over North Korea's apparent plans to test-fire one of its long-range missiles.

The Missile Defense Agency says its own test had been scheduled for months and was not prompted by the North Korean situation.

In today's rescheduled test, the Pacific Missile Range Facility on Kaua'i is due to fire a medium-range dummy target into the air off Hawai'i.

A Navy cruiser would then detect the target and launch a Standard Missile-3 interceptor to shoot it down.

A Japanese ship has been sent to practice tracking the target, the first time one of Tokyo's vessels has participated in a U.S. missile defense test.