The U.S. is beefing up its missile defense system in response to North Korea's latest threats.

The Pentagon announced today it will spend $1 billion to add 14 interceptors in Alaska, responding to what it calls faster-than-anticipated North Korean progress on nuclear weapons and missiles.

In announcing the decision, Defense Secretary Chuck Hagel acknowledged the interceptors already in place to defend against potential missile strikes have had poor test performances.

Hagel says he's determined to protect the U.S. homeland and stay ahead of a worrisome North Korean missile threat.

The 14 additional interceptors will be installed at Fort Greely, Alaska, where 26 already stand in underground silos.

Hagel says a portion of the $1 billion cost of the expanded system will come from scrapping the final phase of a missile defense system the U.S. is building in Europe.