North Korea (search) marked May Day on Thursday by urging its workers to prepare for war with the United States, while South Korea's president said he will visit Washington to seek a peaceful solution to the nuclear crisis.
At a rally in Pyongyang (search), communist labor leader Ryom Sun Gil (search) called for workers to form regiments and divisions " ... so that they may be fully ready to defend the country from the enemy's invasion," said the North's official news agency, KCNA.
Ryom is chairman of the Central Committee of the General Federation of Trade Unions of Korea.
North Korea claims the United States plans to invade the isolated communist state because of a dispute over the North's suspected development of nuclear weapons.
Washington says it seeks to resolve the nuclear dispute peacefully, but U.S. officials have not ruled out a military option.
On Wednesday, North Korea said it would regard any U.S. move to seek U.N. sanctions (search) against it because of its nuclear ambitions as "the green light to a war."
The nuclear crisis flared late last year when Washington said North Korea admitted running a secret nuclear weapons program in violation of a 1994 treaty.
U.S. officials say North Korea claimed last week that it had nuclear weapons and was contemplating exporting or using them, depending on U.S. actions.
Meanwhile, North Korean leader Kim Jong Il visited a military unit on Thursday to celebrate May Day with soldiers, KCNA said. The North's 1.1 million-strong military, the world's fifth largest, forms the backbone of Kim's totalitarian rule.
Secretary of State Colin Powell (search) said this week the United States was reviewing the North's offer to give up its missiles and nuclear facilities in exchange for substantial U.S. economic benefits. The North Koreans floated the proposal in talks with American envoys in Beijing last week.
Pyongyang also demands a nonaggression treaty with the United States. The U.S. administration has ruled this out, but says some written security guarantee could be possible.