The North Korean military says it has “ratified” a merciless attack against the United States, potentially involving a “cutting-edge” nuclear strike.
“The moment of explosion is approaching fast,” the army said in a statement on state news agency KCNA.
War could break out “today or tomorrow,” the statement said, quoting a spokesman for the General Staff of the Korean People’s Army.
“The merciless operation of (our) revolutionary armed forces in this regard has been finally examined and ratified.
“The US had better ponder over the prevailing grave situation.”
Pyongyang’s latest pronouncement came as Washington scrambled to reinforce its Pacific defences, preparing to move an advanced missile defence system to the island of Guam.
The land-based weapon, which is primed to shoot down short and medium-range missiles, will be sent to the US territory to defend its bases there.
The Pentagon has already sent bombers, stealth aircraft and ships.
Tensions have been soaring on the Korean peninsula since the North launched a long-range rocket in December and conducted its third nuclear test in February.
North Korea has threatened missile and nuclear strikes against the US and South Korea in response to UN sanctions and joint military drills.
US Defence Secretary Chuck Hagel said earlier on Wednesday that North Korea’s “bellicose dangerous rhetoric” posed a “real and clear danger” to America and its allies South Korea and Japan.
“They have nuclear capacity now, they have missile delivery capacity now,” he said.
“We take those threats seriously, we have to take those threats seriously.
“We are doing everything we can, working with the Chinese and others to defuse that situation on the peninsula.
“I hope the North will ratchet its very dangerous rhetoric down.”
And in another escalation in the crisis, North Korea on Wednesday blocked access to the key Kaesong joint industrial zone with South Korea.
Any move on Kaesong – established in 2004 and a crucial source of hard currency for North Korea – carries enormous significance.
Neither of the Koreas has allowed previous crises to significantly affect the complex, which is the only surviving example of inter-Korean cooperation and seen as a bellwether for stability on the Korean peninsula.
China, the North’s sole major ally, appealed for “calm” from all sides, repeating Beijing’s oft-declared position.