Intelligence officials suspect that Russia, Pakistan and China are suppliers of equipment North Korea has used to develop its nuclear weapons program, an allegation Moscow and Islamabad quickly denied Friday.
"This has absolutely nothing to do with reality," said Russian Foreign Ministry spokesman Alexander Yakovenko.
"No exchange of any sort was done with North Korea," said Gen. Hamid Gul, a former chief of Pakistan's spy agency, Inter-Services Intelligence. "North Korea's technology has always been ahead of ours ... North Korea has always been close to China and Russia ... we are in no position to help them."
Two U.S. officials said Friday that while China is believed to be among North Korea's sources, Pakistan and Russia are its main suppliers of equipment needed to enrich uranium for nuclear weapons. Some of the equipment has industrial as well as military uses and passes through countries which may not know what North Korea is doing with it.
White House spokesman Ari Fleischer would not comment on a New York Times report that Pakistan, in the late 1990s, forged a deal supplying Pyongyang with the equipment in exchange for North Korean missiles.
But he said: "Since Sept. 11, many things that many people may have done years before Sept. 11 ... have changed." Pakistan has become a major ally among the 90-nation anti-terror coalition established since the Sept. 11 attacks on America.
Another official, asking not to be identified, confirmed that Pakistan has carried out exchanges with North Korea on weapons technology but said they took place before President Pervez Musharraf took office in 1999.
Pressing suppliers to deprive North Korea of nuclear-related equipment will have to be part of the intense diplomatic effort launched by the Bush administration, since North Korea startled officials with the admission it has been secretly pursuing its nuclear program despite agreeing not to, one analyst said.
The administration is working to form an international coalition to steer North Korea away from its decision to pursue nuclear weapons.
"I think we're going to see that no one wants to have a nuclear-armed North Korea," Condoleezza Rice, Bush's national security adviser, said Thursday night on ABC's Nightline.
"Effective international pressure may have an effect on North Korea," she said, adding that China, Russia, South Korea and Japan could fill that role.
Sen. John McCain said Friday he thought economic sanctions ought to be leveled immediately against Pyongyang.
"I'm not ruling out the military," he said on NBC's Today show, "but there are other actions that would have to be tried first. And I believe that strong economic sanctions could bring down that government."
The U.S. diplomatic offensive began not long after the administration disclosed Wednesday that North Korea had acknowledged, during bilateral talks earlier this month, that it was attempting to develop nuclear weapons.
Two top State Department officials, John Bolton and James Kelly, flew to Beijing for talks Thursday with Chinese officials.
China is 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.
President Bush is expected to raise the issue with Chinese President Jiang Zemin next week when they meet at Bush's ranch in Texas.
Kelly plans consultations in Japan and South Korea on North Korea. Bolton's itinerary includes stops in Russia, Britain and France, all nuclear powers which may have views on how to influence North Korea.
Chang-beom Cho, South Korea's deputy foreign minister for policy planning, said Friday in Washington his government was involved in "intensive consultations" with the United States and Japan on what to do about the threat posed by North Korea's nuclear weapons program.
"We are urging North Korea to fully comply with their commitment to the Nuclear Non-Proliferation Treaty and also with a South-North agreement signed a decade ago on de-nuclearization of the Korean peninsula," he said.
Cho said he hoped the threat "will be wisely dealt with, hopefully through peaceful means and intensive dialogue soon as possible."
Secretary of State Colin Powell said the United States had no plans to undertake military action against North Korea.
Rice suggested it would be a mistake to equate the situation in North Korea with that of Iraq, where the United States is contemplating use of force to disarm that country.
"We've tried everything with Saddam Hussein. Nothing has worked," she said.
North Korea's nuclear program came to light when a U.S. delegation confronted North Korea with evidence gathered over the past several months, including recent bills of sale, that Pyongyang had been working to enrich uranium for nuclear weapons, officials said.
That equipment most likely was part of a gas centrifuge program to separate weapons-grade uranium from ordinary fuel-grade uranium, private analysts said Thursday.
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.
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.
But Defense Secretary Donald H. Rumsfeld told a Pentagon news conference Thursday he believes the North Koreans already have produced "a small number" of the weapons.