SEOUL, South Korea -- North Korea declared it is strengthening its "nuclear deterrent," raising the stakes Wednesday in its standoff with South Korea and the United States.
South Korea's interim leader called for a stronger alliance with Washington, dismissing a claim by the North that the South's parliamentary im-peachment of President Roh Moo-hyun last week reflected U.S. interference to "install an ultra-right pro-U.S. regime" in Seoul.
With the unprecedented impeachment spawning uncertainty, South Korea has ordered heightened military vigilance against the North. It is also going ahead with annual joint military exercises with the United States, scheduled to begin Sunday, to test the allies' defense readiness.
Pyongyang on Wednesday accused Seoul of "kicking up a racket of confrontation with the North."
"This attitude ... is a grave provocation to the compatriots in the North," said North Korea's Committee for the Peaceful Reunification of the Fatherland, a government agency handling relations with the South.
There are fears that Pyongyang may use the South's leadership crisis to stall six-nation nuclear talks aimed at defusing the nuclear standoff.
North Korea said Wednesday it was strengthening its "nuclear deterrent" -- its term for nuclear weapons development.
The North blamed the United States for the lack of breakthroughs in last month's six-nation talks, and accused Washington of raising tensions on the Korean peninsula by holding the joint military exercises.
Washington and Seoul say the annual drills, which run through March 28, are routine exercises.
"The Korean people, who consider independence to be their life and soul, are keeping a close eye on the U.S. moves, while further strengthening the self-defense nuclear deterrent to cope with them," said North Korea's official news agency, KCNA.
A second round of six-nation talks ended in Beijing in late February with little progress. Washington insisted on a "complete, verifiable and irreversible dismantling" of all the North's nuclear facilities. Pyongyang said it would dismantle its nuclear programs only if the United States provides economic aid and security guarantees.
The talks involved the United States, the two Koreas, China, Russia and Japan. They agreed to meet again by July.
Prime Minister Goh Kun -- who is leading South Korea's government until the Constitutional Court rules on whether to oust Roh or to restore his suspended presidential powers -- moved quickly to dismiss the North's threats.
Amid political uncertainty, "establishing a solid security posture is more important than anything else," Goh said in a speech Wednesday at the Air Force Academy's graduation ceremony.
"We must further strengthen our alliance with the United States," he said.
South Korea's parliament voted Friday to impeach Roh for alleged election-law violations and incompetence. The Constitutional Court has 180 days to rule.
North Korea has bitterly denounced the impeachment, initiated by South Korea's conservative opposition -- which favors a tougher stance toward the North.
"The U.S. is chiefly to blame for the incident," KCNA said. "The U.S. egged the South Korean political quacks, obsessed by the greed for power, on to stage such incident in a bid to install an ultra-right pro-U.S. regime there."
About 1,500 people protested the impeachment Wednesday night in Seoul. The number of protesters was sharply lower than the 50,000 who gathered over the weekend to hold candles and chant for Roh's reinstatement.