The Pentagon announces it will increase the number if interceptors in its West Coast missile defense system by 14. Thirty are already in place, 26 at Fort Greeley Alaska and 4 at Vandenberg AFB in California.
The defensive military action comes after North Korea tested an underground nuclear device launched a small satellite into orbit for the first time and displayed what US intelligence believes may be a road-mobile ballistic missile.
Experts say a complex detection system of satellites and radar would detect an enemy missile and launch an interceptor if needed.
The increase in defense aims to protect the US as well as its NE Asia allies.