"The madcap nuclear war moves against the DPRK (North Korea) are extremely reckless proactive acts that make the nuclear issue on the Korean peninsula all the more difficult to resolve and drive the situation to its worst," the Korea National Peace Committee said in a statement carried on the North's KCNA news agency.
The statement also said the North's own nuclear test was part of preparations to defend itself against an US attack. It claimed US outrage over the regime's test was a smokescreen for its own war plans.
"The people and its army are prepared for any provocations, any nuclear war moves," it said.
It warned South Korea against relying on the United States for protection which would only make the country more vulnerable to an attack.
North Korea carried out its first nuclear test on October 9, sparking international condemnation and UN Security Council sanctions.
South Korea says it will consider revising its policy of reconciliation toward the North to bring it more in line with international sanctions.
Under a joint military alliance, the United States has reaffirmed its commitment to extend a nuclear umbrella over South Korea amid an escalating nuclear threat from North Korea.
Seoul reportedly wants Washington, which withdrew all its nuclear weapons from the Korean peninsula in 1991, to elaborate on what types of tactical nuclear weapons could be provided under the deterrent strategy.
South Korea gave up its quest for nuclear weapons in the 1970s under strong US pressure.
The US has stationed tens of thousands of troops in South Korea ever since the 1950-53 war sparked by an invasion from the North.

Copyright AFP (Agence France-Presse), 2006