"The moment of explosion is approaching fast," the North Korean military said, warning that war could break out "today or tomorrow".
In response, President Obama ordered a ballistic missile defence system be moved to the nearest U.S. military base to the rogue state.
The U.S. defence system will move to Guam, the nearest American military base to North Korea, 2,000 miles south east of Pyongyang in the Pacific Ocean.
U.S. defence secretary, Chuck Hagel, said: “Some of the actions they have taken the last few weeks present a real and clear danger and threat to the interests of our allies starting with South Korea and Japan.
“Also there have been threats the North Koreans have leveled at our base in Guam and Hawaii.”
He added: "We are doing everything we can to defuse that situation on the peninsula.
"I hope the North will ratchet this very dangerous rhetoric down," he said, adding that there is a way to peace but only if Kim Jong Un decides to be "a responsible member of the world community."
The U.S. had earlier moved two warships to the western Pacific to be on alert for missiles and conducting bomber and fighter flyovers
The latest ploy by rogue nuclear state was banning South Korean workers from the jointly run Kaesong industrial zone.
More than 800 South Koreans who had stayed overnight at the complex were being allowed to return home, but that new workers were not being allowed across the border.
Kaesong, a major source of income for the impoverished, communist North, is home to 124 South Korean companies that employ 53,000 North Korean workers in a cross-border, heavily fortified joint enterprise.
Permission is granted on a daily basis for South Korean workers to cross into the complex, situated in the North.
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