The warning from an unnamed army spokesman and carried by Pyongyang's state-run news agency was latest in a series of escalating threats 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.
Washington calls the military drills, which this time have incorporated nuclear-capable stealth bombers, routine annual exercises between the allies. Pyongyang calls them rehearsals for a northward invasion.
The foes fought on opposite sides of the three-year Korean War, which ended in a truce in 1953. The divided Korean Peninsula remains in a technical state of war, and Washington keeps 28,500 troops in South Korea to protect the ally.
The military statement said North Korean troops had been authorized to counter U.S. aggression with "powerful practical military counteractions," including nuclear weapons.
However, North Korea's nuclear strike capabilities remain unclear. Pyongyang is believed to be working toward building an atomic bomb small enough to mount on a long-range missile but is thought to be several years from being capable of mastering the technology.
Copyright 2013 The Associated Press.