It also continued to target South Korean President Lee Myung-bak, calling him a traitor, a day after U.S. Secretary of State Hillary Clinton warned that ties with Pyongyang could not improve if it continued insulting South Korea.

North Korea's official media, however was silent on Clinton's remarks over the leadership issue in Pyongyang and the possibility of a crisis over who may succeed leader Kim Jong-il, 67, who is widely believed to have suffered a stroke last August.

"If the U.S. war-thirsty forces are allowed to continue frantically stepping up the moves for another Korean war ... the situation on the Korean Peninsula will reach an unpredictable phase and the U.S. will be held wholly accountable for the ensuing consequences," the North's official Rodong Sinmun newspaper said.

Clinton on Friday called the North a "tyranny" and demanded it stop insulting the leaders in the South if it wanted a normal relationship with Washington.

But North Korea's agency that handles dealings with the South said Lee had insulted the socialist state ideology of the North and erased all chances of improving ties between the two states.

"We will settle scores with the traitor with the most merciless and resolute determination," the North's Committee for the Peaceful Reunification of the Fatherland said in a statement.

North Korea has issued increasingly furious rhetoric against the South in anger over conservative policy to get tough with Pyongyang and stop the no-questions-asked aid given by his liberal predecessors.

Clinton said on Thursday questions about the North's leadership succession created uncertainty and possibly encourage provocative behaviour inside the communist state.

North Korea has been thought to be readying its longest-range missile for launch in what analysts said is a bid to grab the new U.S. administration's attention and put pressure on Seoul.

Clinton was in Beijing on Saturday on the final leg of her tour which also took her to Japan, South Korea and Indonesia.