Updated

North Korea's declared determination to become the world's eighth nuclear power has prompted a flurry of U.S. diplomatic activity as the Bush administration, its policy of engagement with Pyongyang having run aground, ponders its next steps.

Undersecretary of State John Bolton met Thursday with officials in China, a major trading partner of North Korea's and perhaps the one country capable of extracting concessions from the communist nation through economic sanctions, an administration official said.

At the White House, reporters were told the Chinese were stunned upon learning of North Korea's acknowledgment to U.S. officials that it was pursuing a nuclear weapons program.

A U.S. delegation had confronted North Korea with evidence gathered over the last several months, including recent bills of sale, that Pyongyang had been working to enrich uranium for nuclear weapons. That equipment most likely was part of a gas centrifuge program to separate the weapons-grade uranium from ordinary fuel-grade uranium, private analysts said Thursday.

The New York Times said U.S. intelligence officials have concluded that Pakistan was a major supplier of equipment North Korea needed to restart its nuclear program. In return, North Korea supplied Pakistan with missiles it could use to counter India's nuclear arsenal, the report said.

China and Russia were less prominent suppliers of equipment for North Korea's nuclear program, the report said. It cited unidentified current and former senior U.S. officials.

A U.S. intelligence official said late Thursday he could not confirm the report.

North Korea's earlier nuclear efforts relied on plutonium, which makes smaller, lighter bombs but is much more difficult to produce and work with than enriched uranium.

White House spokesman Scott McClellan said President Bush believes North Korea's admission is "troubling, sobering news." He said Bush is seeking a peaceful solution.

Privately, White House officials said Bush and his senior advisers decided to confront the problem in a low-key fashion. Bush, for example, made no public statements on it Thursday.

Stressing the diplomatic approach, national security adviser Condoleezza Rice said, "I think were going to see that no one wants to have a nuclear-armed North Korea and that effective international pressure may have an effect on North Korea."

Rice suggested it would be a mistake to equate the situation in North Korea with that of Iraq, a country the United States is contemplating using force to disarm.

"We've tried everything with Saddam Hussein. Nothing has worked," she said.

China, Russia, Japan and South Korea are among the countries which have a stake in a nuclear-free North Korea, Rice said in an interview taped for the Thursday edition of ABC's "Nightline."

Secretary of State Colin Powell told a news conference in New York the United States was not planning military action against North Korea at present.

The North Koreans told U.S. officials earlier this month that they no longer consider valid a 1994 agreement with the United States under which Pyongyang promised to renounce nuclear weapons.

It was not clear to U.S. officials whether the North actually has a nuclear capability or whether it is still in development. At a minimum, North Korea apparently is close to joining the United States, China, Russia, Britain, France, India and Pakistan as declared nuclear powers. Israel is thought to have hundreds of nuclear warheads but has never confirmed it has a nuclear weapons program.

Secretary of Defense Donald H. Rumsfeld told a Pentagon press conference that he believes the North Koreans not only have a weapons program but have already produced some weapons.

He cited an intelligence report in which the CIA said North Koreans "may have one or two," and added, "I believe they have a small number of nuclear weapons."

Senate Majority Leader Tom Daschle, D-S.D., said North Korea must allow international inspections of their nuclear facilities and must agree to destroy whatever weapons of mass destruction they have.

"Pyongyang's reckless brinkmanship must be met with firm and united resolve by the allies of freedom and democracy," said Rep. Henry Hyde, R-Ill., chairman of the House International Relations Committee.

U.S. officials said they believe a nuclear-armed North Korea would alarm China because it would prompt Japan, China's historic rival, to carry out a military buildup of its own, forcing China to respond in kind.

After his meetings in China, Bolton also planned to travel to Russia, Britain and France to discuss how to bring pressure to bear on North Korea.

Assistant Secretary of State James Kelly was in Beijing with Bolton and planned subsequent stops in Japan and South Korea.

Kelly led the U.S. delegation to Pyongyang from Oct. 3-5 that confronted North Korean officials with information that the North was developing nuclear weapons in violation of the 1994 agreement.

At first the North Koreans denied the allegation but then acknowledged at the final meeting, on Oct. 4, that Kelly's contention was correct.

Powell said the North Koreans tried to blame the United States for their decision to renege on their promises.

But, Powell said, "we pointed out to them that this violation of theirs preceded this administration and has been going on for years."

As for why the North Koreans made the admission, Henry Sokolski of the Nonproliferation Policy Education Center, said Pyongyang may see the bombs as a deterrent against a pre-emptive strike by the United States. Also, he suggested, Pyongyang may reason it can get away with the disclosure now because the United States is too focused on Iraq to take action.

At the meeting, the North Koreans' demeanor and tone was especially belligerent and vitriolic, a separate U.S. official said, but added that they made no threat against any specific country. Instead, they uttered vague threats such as, "We will meet the sword with the sword."

Even without nuclear weapons, North Korea boasts a formidable military establishment. It has chemical and biological weapons deployed near the Demilitarized Zone and its troop strength is the fifth-largest in the world, with more than 1.17 million personnel, according to Pentagon estimates. It also has 200-300 interceptors and attack aircraft, including the MiG-21s and MiG-23s.

Even though the North Korea repudiated the 1994 agreement, the Bush administration was not ready to announce its death, preferring to consult with other countries first.

Officials said the administration is talking with allies about shutting down a program under which the United States provides North Korea with 500,000 tons of heating oil annually.

The program is designed to help North Korea meet its energy needs during a transition period before the planned construction of two light water nuclear reactors, with financing mostly by South Korea and Japan.

Those reactors were also part of the 1994 deal to bring about a nuclear weapons-free North Korea but that plan seems certain to be scrapped because of Wednesday's disclosures about Pyongyang's weapons plans.