The United States said it was not surprised by the North Korean move. South Korea called the nuclear standoff a matter of "life and death." China, the North's closest ally, urged negotiations.

Washington said North Korea already was violating the 1968 Nuclear Nonproliferation Treaty by secretly pursuing weapons development and flouting U.N. safeguards. The United States believes the North already has one or two nuclear bombs.

"The North Koreans were not adhering to the treaty when they were still a party to it," said Undersecretary of State for Arms Control John Bolton, who was visiting Thailand.

The communist country said it had quit the treaty because of alleged U.S. aggression, but said it had no intention of producing nuclear weapons and would use its nuclear program only for peaceful purposes "at this stage."

The North's declaration heightened tension as the United States and its allies seek a diplomatic solution. Pyongyang's action could mean the North is trying to force the United States to make concessions, including a nonaggression treaty and economic aid.

The Bush administration, awaiting the outcome of talks in New Mexico, said North Korea must completely dismantle its nuclear weapons program.

"The only message we expect is what America's position is, that we are ready to talk, and that we will not negotiate," presidential spokesman Ari Fleischer said.

Gov. Bill Richardson, a former U.N. ambassador, was expected to push that message during a second day of discussions Friday in Santa Fe with two North Korean U.N. diplomats. They met for two hours over dinner on Thursday.

"The talks were cordial but candid," said Richardson's spokesman, Billy Sparks. Richardson visited North Korea on two diplomatic missions while he was still a member of Congress during the 1990s.

China said it worried about the consequences of its longtime ally's decision to jettison the treaty. In a statement carried by the official Xinhua News Agency, the government said it wants to see a peaceful settlement of the dispute.

"We are concerned about the DPRK's announcement to withdraw from the treaty, as well as consequences possibly caused by the withdrawal," Foreign Ministry spokeswoman Zhang Qiyue was quoted as saying, referring to the North by the initials of its formal name.

As it announced it would pull out of the treaty, a keystone to global nuclear nonproliferation, the North warned the United States not to take military action against it. Pyongyang said a "new Korean War will finally lead to the Third World War" and that the North could hold its own in a "fire-to-fire standoff." The comment was distributed by the official North Korean news agency in English.

The treaty, which the North joined in 1985, requires a withdrawing nation to give three months notice. North Korea, however, said it was withdrawing as of Saturday.

Germany, Australia, Japan, the Philippines and Russia were among countries that expressed deep concern. Britain condemned the North Korean move as "a wrong decision."

South Korean President Kim Dae-jung said dialogue was the only way to solve the nuclear crisis, which he called a matter of "life and death."

His National Security Council held an emergency meeting. Afterward, the Foreign Ministry said the North's withdrawal was a "serious threat to peace and stability on the Korean Peninsula" and urged it to retract its decision.

The nuclear tension could be discussed at Cabinet-level talks between the two Koreas that are scheduled for Jan. 21-24 in Seoul. However, North Korea says the issue is strictly a matter between it and the United States.

In a clear signal it feared losing face, the government said through KNCA:

"We can no longer remain bound to the NPT, allowing the country's security and the dignity of our nation to be infringed upon."

"Though we pull out of the NPT, we have no intention of producing nuclear weapons and our nuclear activities at this stage will be confined only to peaceful purposes such as the production of electricity," the news agency said.

However, analysts say a nuclear reactor in the North Korean town of Yongbyon - the focus of the latest dispute - provides a negligible amount of power. The facility was the centerpiece of a weapons program until it was frozen in a 1994 energy deal with the United States.

U.S. officials said that North Korean negotiators acknowledged in October that they had a second, clandestine nuclear program.

In 1993, North Korea also announced that it was withdrawing from the treaty, but suspended the decision three months later and entered talks with the United States. It again left open the possibility of a negotiated solution.

"If the U.S. drops its hostile policy to stifle the DPRK and stops its nuclear threat to it, the DPRK may prove through a separate verification between the DPRK and the U.S. that it does not make any nuclear weapons," the North Korean government statement said.

DPRK stands for Democratic People's Republic of Korea, the communist state's official name.

However, the North's defiant posture raises the possibility that the International Atomic Energy Agency will send the matter to the U.N. Security Council, which could choose to impose economic sanctions. Such a step could lead to more defiance from the isolated North.

The crisis worsened last month when Pyongyang expelled U.N. inspectors at the Yongbyon site and said it was reactivating the facilities. Experts say North Korea could make several more bombs within six months if it extracts weapons-grade plutonium from spent fuel rods.

North Korea joined the Nuclear Nonproliferation Treaty in 1985. In 1994, North Korea agreed to freeze its nuclear facilities at Yongbyon under an energy deal with the United States. Those facilities are the focus of the new crisis.

Only four other countries - Cuba, India, Israel and Pakistan - are not signatories, though Cuba is a member of a treaty establishing a nuclear-free zone in Latin America.

A U.N. relief official, meanwhile, appealed for more food aid for North Korea as part of the World Food Program's plans to feed 6.5 million North Koreans this year, said Richard Corsino, the WFP's director for North Korea. The isolated, Stalinist dictatorship has relied on foreign food aid since the mid-1990s.

"We don't have enough contributions at this point to give us any degree of confidence that we will be able to meet our targets for the first half of this year," said Corsino, who stopped in Beijing after a visit to WFP headquarters in Rome.