W By Peter Slevin and Karen DeYoung

ASHINGTON – The North Korean government has acknowledged for the first time that it has been secretly developing nuclear weapons for years in violation of international agreements – and that it possesses “more powerful” weapons, as well – Bush administration officials said Wednesday night.

The North Koreans, who confirmed the project when challenged by visiting U.S. diplomats earlier this month, said the existence of the program nullifies a 1994 deal with the United States to halt their nuclear weapons program in return for foreign help. One senior U.S. official said the new weapons project is a “very serious material breach” of the accord.

The Bush administration, stunned by the admission, dispatched envoys to the region Wednesday to consult with allies and called on North Korean leader Kim Jong Il to halt the weapons project. The administration also has begun consultations with Congress about what to do next.

“The United States is calling on North Korea to comply with all of its commitments under the Non-Proliferation Treaty and to eliminate its nuclear weapons program in a verifiable manner,” a U.S. official said. “What we seek is a peaceful resolution of this situation.”

The revelation from the isolated Stalinist country presents the Bush administration with a serious, unanticipated foreign policy challenge as officials prepare to confront Iraqi President Saddam Hussein over his refusal to surrender weapons of mass destruction. Meanwhile, thousands of U.S. troops remain deployed in an unstable Afghanistan and terrorist attacks have spiked in recent weeks from Yemen to Indonesia.

U.S. officials and commentators offered differing assessments Wednesday night of the implications of North Korea’s announcement, with some considering it a belligerent act deserving of a strong response, and others saying it could be a bid by North Korea to create an opening to the United States.

“This is going to require a reassessment of our commitments to North Korea,” said Sen. Bob Graham, D-Fla., chairman of the Senate intelligence committee. “It’s a very serious development if a country we had thought had entered into a serious and credible negotiation to retreat from a nuclear program in exchange for generous assistance” has violated that agreement.

President Bush counts North Korea as a member of an “axis of evil,” along with Iraq and Iran. Yet the revelation of the nuclear program comes amid a string of surprisingly conciliatory moves by Kim, long criticized for peddling dangerous weapons and oppressing an impoverished population. In recent weeks, the Pyongyang government apologized for a naval battle with South Korea in the Yellow Sea and for the abduction of Japanese citizens in the 1970s.

A U.S. delegation headed by Assistant Secretary of State James Kelly presented detailed evidence of a covert nuclear weapons program during an Oct. 3-5 trip, U.S. officials said. The North Koreans called the allegations “fabrications,” but then a day later, a more senior official, Deputy Foreign Minister Kang Sok Joo, confirmed Kelly’s charges. He said the North Koreans met through the night before deciding to reveal that the project had been underway for several years. He also said his government had developed other, more powerful weapons.

Kang offered no apologies. He was “assertive, aggressive about it,” a U.S. official said.

The administration says it does not know the full extent of North Korea’s nuclear capabilities, and experts are uncertain what Kang meant when he referred to more powerful weapons. Wednesday night, they said they assume he meant weapons of mass destruction, which typically include biological and chemical weapons.

North Korea’s new nuclear project relies on highly enriched uranium, a switch from an earlier plutonium-based program that Pyongyang agreed to halt in the groundbreaking 1994 Agreed Framework. U.S. officials would not answer when asked whether the highly enriched uranium had yet been turned into a weapon.

The CIA’s National Intelligence Estimate, released in December, reported that North Korea had likely produced one or two plutonium-based nuclear weapons by the mid-1990s.

Administration officials have struggled with the North Korean policy since Bush took office, with some officials advocating a much more demanding approach than the engagement policy of the Clinton administration and others urging continued diplomatic flexibility.

The disclosure has not ended that debate, said one high-ranking official, who reported that some administration leaders believe “we should go to war tomorrow.” He added, however, that Bush has been “very calm, cool and collected. He doesn’t need another crisis.”

The North Korean disclosure was “a jaw-dropper,” said the official. It revealed a worrisome determination to build a nuclear device, but it also left open the possibility that Kim, who has been repairing relations with foreign rivals, unveiled the project as a way of coming clean.

The admission “represented a candor on the part of North Korean officials that we are unaccustomed to,” the official said. “It has promise. It has opportunity. It has dangers.”

For now, the administration is suspending its offer to engage North Korea – a pledge of an economic and political opening in return for reductions in North Korea’s military posture and policies of weapons proliferation, along with an improvement in humanitarian conditions.

“In light of our concerns about the nuclear weapons program, we could not pursue that approach,” a U.S. official said during the conference call. “Everyone in the region has a stake in this issue, and no peaceful nation wants to see a nuclear-armed North Korea.”

Joseph Cirincione, director of the non-proliferation project at the Carnegie Endowment for International Peace, said the administration faces two very distinct choices. “They either play `gotcha”‘ and cut off relations, he said, “or they can justifiably claim that their tough approach produced exactly the change in North Korean behavior we had been seeking.”

Cirincione noted that as the United States has begun its campaign against Iraq, “North Korea has taken some surprising steps just in the last three months. They are not changing regimes but they are making change in their regime.”

In Japan, Prime Minister Junichiro Koizumi’s spokeswoman, Misako Kaji, said, “Japan is gravely concerned” about the U.S. announcement North Korea is developing nuclear weapons.

The parallels between North Korea and Iraq are worth noting, said Henry Sokolski, executive director of the Non-Proliferation Education Center. He pointed to the administration’s repeated assertions that Iraq will not be secure until Saddam is removed from power.

“If we’re serious about Iraq, as we are and should be, we need to be twice as serious as we currently are about North Korea,” said Sokolski, who believes the administration should be tough on Kim. “If you’ve got a nuclear cheater, do you give them the benefit of the doubt and coddle him? Or do you say the burden’s on you to come clean?”