Seoul: North Korea today threatened a "sacred war" over US-South Korean joint military drills next week as a US envoy urged Pyongyang's new leadership to engage in dialogue with the outside world.

The North's National Defence Commission (NDC) denounced the annual joint exercises as a "silent declaration of war," describing them as "unpardonable war hysteria."

Key Resolve, a computerised command post exercise, will start on Monday and continue until March 9. Separately, the joint air, ground and naval field training exercise Foal Eagle will be held from March 1 to April 30.

"Key Resolve and Foal Eagle are unpardonable war hysteria kicked up by the hooligans to desecrate our mourning period and an unpardonable infringement upon our sovereignty and dignity," the NDC said in a statement.

"Our army and people will foil the moves of the group of traitors to the nation and warmongers at home and abroad for a new war with a sacred war of our own style," the NDC said, indicating it would stage a counter exercise.

The threat is the latest instance of Pyongyang taking a hostile tone towards Seoul since Kim Jong-Un, the youngest son of the late leader Kim Jong-II, took over after his father Kim
Jong-II died of a heart attack on December 17.

Last week the North vowed "merciless retaliatory strikes" if any shells landed in waters claimed by Pyongyang during a live-fire artillery exercise near the disputed Yellow Sea border. But, in the event it took no military action in response to the drill.

"War manoeuvres... are, in essence, a silent declaration of a war. The declaration of the war is bound to be accompanied by a corresponding physical retaliation," the NDC said on Saturday.

"Now that a war has been declared against us, the army and people are firmly determined to counter it with a sacred war of our own style and protect the security of the nation and the peace of the country," it added.

It accused "US imperialists" of intensifying moves to ignite a war, and implied that the North had the capacity to strike against the US mainland.

"Nuclear weapons are not the monopoly of the US. We have war means more powerful than the US nukes and ultra-modern striking equipment which no one has ever possessed," it said.