In what engineers called a first, the U.S. military destroyed two ballistic missile targets simultaneously in space 100 miles (161 kilometers) above the Pacific Ocean in a test.

Engineers said it was the first time the U.S. missile defense system had shot down two ballistic missile targets at once.

The USS Lake Erie fired two interceptors to shoot down two short-range ballistic missiles fired within minutes of one another from a testing range on the Hawaiian island of Kauai.

The targets were short-range missiles and did not separate in flight, unlike longer range missiles.

The event builds on an April test in which a Navy ship intercepted one cruise missile and one ballistic missile.

But Tuesday's test was more challenging because ballistic missiles travel at greater speeds and higher altitudes than cruise missiles, making them harder to shoot down.

"The tests are set up to have more and more operational realism," said Joseph Rappisi, director of maritime missile defense programs at Lockheed Martin.

The test marked the 10th and 11th successful intercepts by the Aegis ballistic missile defense system in 13th attempts, the Missile Defense Agency said in a statement.

Aegis was developed as an integrated radar and missile system for the Navy some 40 years ago but has since been modified to enable ships to track and shoot down ballistic missiles.

By 2009, the U.S. Navy plans to install ballistic missile tracking and interception capabilities on 18 cruisers and destroyers. Sixteen of the vessels are assigned to the Pacific Fleet.

A Japanese navy Aegis-equipped ship, the Kongo, joined Tuesday's test by tracking the missile targets.

The Kongo also simulated firing its own interceptors in preparation for another test off Hawaii next month in which it will attempt to intercept a missile itself. If successful, the event would mark the first time Japan has ever intercepted a ballistic missile.