U.S. Secretary of State Hillary Rodham Clinton, right, signs the Treaty of Amity and Cooperation along with others at the end of the 17th ASEAN Regional Forum Friday in Hanoi, Vietnam.

Hanoi, Vietnam ? North Korea threatened today to mount a powerful nuclear response to upcoming joint U.S.-South Korean military drills, calling the exercises an “unpardonable” provocation on top of wrongly blaming Pyongyang for the sinking of a South Korean warship.

North Korea’s powerful National Defense Commission, led by leader Kim Jong Il, warned that its troops would counter the move to hold military maneuvers involving a nuclear-armed U.S. supercarrier with a “retaliatory sacred war.”

“The army and people of the DPRK will legitimately counter with their powerful nuclear deterrence the largest-ever nuclear war exercises to be staged by the U.S. and the south Korean puppet forces,” North Korea’s official news agency in Pyongyang quoted an unnamed commission spokesman as saying, referring to the country by its official name, the Democratic People’s Republic of Korea.

Pyongyang routinely threatens war when South Korea and the U.S. hold joint military drills, which North Korea sees as a rehearsal for an attack on the North. The U.S. keeps 28,500 troops in the South to deter against aggression, but says it has not intention of invading the North.

U.S. Defense Secretary Robert Gates and South Korean Defense Minister Kim Tae-young announced earlier this week in Seoul that the allies would stage a massive four-day military show of force starting Sunday to send a “clear message” to North Korea to stop its aggressive behavior.

Washington and Seoul blame Pyongyang for the deadly sinking of a South Korean warship in the waters off Korea’s west coast. Forty-six sailors were killed in what Seoul calls the worst military attack on South Korea since the 1950-53 Korean War.

North Korea vehemently denies any involvement, and has warned that any punishment would trigger war.

In Vietnam for a Southeast Asian regional security forum, U.S. Secretary of State Hillary Rodham Clinton traded barbs with a North Korean official over the sinking, the military drills and the imposition of new U.S. sanctions against the North.

Also Friday, the U.S.-led military command monitoring the cease-fire on the Korean peninsula confronted the North about the March 26 sinking of the warship Cheonan, calling it a violation of the armistice signed in 1953. Colonels from the U.N. Command, who met at the border with counterparts from the North’s army, reminded them of the U.N. Security Council order to honor the truce. Officers also proposed a joint task force to discuss armistice violations, the military commission said in a statement.

A team of international investigators concluded in May that a North Korean submarine fired the torpedo that sank the Cheonan. The U.N. Security Council approved a presidential statement this month condemning the sinking, but did not directly blame Pyongyang.

At the Association of Southeast Asian Nations meeting in Hanoi, North Korean spokesman Ri Tong Il repeated Pyongyang’s denial of responsibility for the sinking. He said the upcoming military drills — to be conducted in the Sea of Japan off Korea’s east coast and in the Yellow Sea closer to China’s shores — were a violation of its sovereignty that harked back to the days of 19th-century “gunboat diplomacy.”

The exercises will be “another expression of hostile policy against” North Korea. “There will be physical response against the threat imposed by the United States militarily,” Ri told reporters.

Clinton responded by saying the U.S. is willing to meet and negotiate with the North, but that this type of threat only heightens tensions. She added that progress in the short term seems unlikely.

“It is distressing when North Korea continues its threats and causes so much anxiety among its neighbors and the larger region,” she told reporters. “But we will demonstrate once again with our military exercises … that the United States stands in firm support of the defense of South Korea and we will continue to do so.”