The new US Defense Secretary, Chuck Hagel, has announced a plan to bolster the country's missile defenses in Alaska and California.

Hagel says the move is aimed at countering the growing threat from the Democratic People’s Republic of Korea.

The Pentagon is planning to add 14 interceptor missiles to the 30 already in place in the two states, expanding the system’s ability to shoot down long-range missiles.

Hagel’s announcement comes a week after the DPRK threatened the US with a pre-emptive nuclear strike. Last month, Pyongyang conducted its third nuclear test, in defiance of U.N. resolutions.