The agency said in a statement Friday that a C-17 airplane successfully deployed the target missile but the target's rocket motor didn't ignite.
A missile interceptor fired from the Terminal High Altitude Area Defense system at the Pacific Missile Range Facility on Kauai was supposed to shoot down the target. But it didn't launch when the target missile didn't ignite.
The agency says it's investigating why the target missile failed.
The Terminal High Altitude Area Defense system is designed to shoot down ballistic missiles in their last stage of flight.