North Korea's defense chief vowed Sunday to deal "unimaginably deadly blows" to the United States and South Korea if they attack the communist nation amid a tense standoff over Pyongyang's nuclear ambitions.

Defense Minister Kim Yong Chun issued the warning during a national meeting held on the eve of the anniversary of the armistice that ended the 1950-53 Korean War, the official Korean Central News Agency said.

"We will mercilessly and resolutely counter the enemy's sanctions with retaliation, its all-out war with all-out war," Kim told the meeting. "We will deal unimaginably deadly blows at the U.S. imperialists and the South Korean puppets if they ignite a war, obsessed with a foolish ambition."

In a separate dispatch, KCNA also denounced an upcoming military exercise between the U.S. and South Korea as aimed at invading the North. The planned maneuvers lay bear a "black-hearted aim lurking behind" their talk of "dialogue," it said.

North Korea often engages in harsh rhetoric while accusing Washington and Seoul of plotting to invade the nation. Pyongyang says its pursuit of atomic bombs are to defend against what it calls "U.S. nuclear threats."

Washington and Seoul have disavowed any intention of invading the North and say their military drills are purely defensive.

The North's latest warning came as tension runs high following its nuclear and missile tests and U.N. sanctions.

North Korea says it will never return to six-nation talks aimed at ending its nuclear programs.

But Pyongyang's ambassador to the United Nations, Sin Sun Ho, suggested the regime is interested in direct talks with Washington, saying Friday the country is "not against a dialogue" or "any negotiation for the issues of common concern," according to Japan's Kyodo News agency.

The North's main Rodong Sinmun newspaper also said Sunday that the country's envoy told an Asian security conference held in Thailand last week that the nuclear standoff was a matter only between Pyongyang and Washington.

The United States says it is willing to hold direct talks with the North within the six-nation process if it returns to the negotiating table and takes irreversible steps for denuclearization.

The stalled negotiations involve China, Japan, the two Koreas, Russia and the U.S.