North Korea has reportedly said that it has authorized what it terms merciless military strikes on the United States, involving the possible use of what the North is calling cutting-edge nuclear rockets.

The White House has issued the following reaction:

We’ve seen today’s statement by North Korea, again making unhelpful and unconstructive threats. It is yet another offering in a long line of provocative statements that only serve to further isolate North Korea from the rest of the international community and undermine its goal of economic development. North Korea should stop its provocative threats and instead concentrate on abiding by its international obligations.

Earlier today, Defense Secretary Chuck Hagel said, "As they have ratcheted up (their) bellicose, dangerous rhetoric -- and some of the actions they've taken over the last few weeks present a real and clear danger and threat to the interests, certainly of our allies, starting with South Korea and Japan."

Below is more from the Associated Press:

PYONGYANG, North Korea (AP) -- The North Korean army is warning Washington that its military has been cleared to wage an attack using "smaller, lighter and diversified nuclear" weapons.

The threat from the unnamed army spokesman early Thursday is latest in a series of escalating warnings from North Korea, which has railed for weeks against joint U.S. and South Korean military exercises taking place in South Korea and has expressed anger over tightened sanctions for a February nuclear test.

The spokesman said in a statement carried by the Korean Central News Agency that troops have been authorized to counter U.S. aggression with "powerful practical military counteractions."