The Pentagon announced on Friday that it will spend $1 billion to add 14 interceptors to a West-Coast-based missile-defense system, responding to what It called "faster-than-anticipated North Korean progress on nuclear weapons and missiles," according to the Associated Press.

"We will strengthen our homeland defense, maintain our commitment to our allies and partners, and make clear to the world that the United States stands firm against aggression," Secretary of Defense Chuch Hagel told a Pentagon news conference.

Hagel discussed that the Pentagon to add the 14 interceptors to 26 already in place in Fort Greely, Alaska. That will expand the system's ability "to shoot down long-range missiles in flight before they could reach U.S. territory. The U.S. also has four missile interceptors at Vandenberg Air Force Base, California.

Hagel said the 14 extras should be in place by September 2017 but will not be deployed until they have been adequately tested.

The threat of a missile strike from North Korea was the rationale for building the missile defense sites in Alaska and California during the administration of President George W. Bush.

"Our concern about Pyongyang's potential intercontinental ballistic missile (ICBM) capability is compounded by the regime's focus on developing nuclear weapons," he said. "North Korea's third nuclear test last month is obviously a serious concern for all nations." James Miller, the U.S. Undersecretary of Defense for policy said.

North Korea recently threatened to reduce Seoul to a "sea of fire" and stage pre-emptive nuclear attacks on Washington.

"North Korea's shrill public pronouncements underscore the need for the U.S. to continue to take prudent steps to defeat any future North Korean ICBM," Miller also said. He added the project would cost about $1 billion.

North Korea also recently took the bold step of scrapping the armistice that stopped the Korean War in 1953. Kim Jong Un, the young leader, and son of Kim Jong Il, has made his feelings of hostility open for the world to see, brashly threatening the United States and South Korea at every turn. In December South Korea elected Park Geun-hye as its new president.  

North Korea's underground nuclear blast it conducted on February 12 was more powerful than its prior detonation, as they used a smaller and lighter device. In response, the U.N. Security Council unanimously voted for new increased sanctions.