In an effort to increase pressure on North Korea, the Bush administration told its Asian allies in briefings earlier this year Pyongyang had exported nuclear material to Libya. That was a significant new charge, the first allegation that North Korea was helping to create a new nuclear weapons state.

But that is not what US intelligence reported, according to two officials with detailed knowledge of the transaction. North Korea, according to the intelligence, had supplied uranium hexafluoride - which can be enriched to weapons-grade uranium - to Pakistan. It was Pakistan, a key US ally with its own nuclear arsenal, that sold the material to Libya. The US government had no evidence, the officials said, that North Korea knew of the second transaction.

Pakistan's role as both the buyer and the seller was concealed to cover up the part played by Washington's partner in the hunt for al-Qaeda leaders, according to the officials, who discussed the issue on condition of anonymity. In addition, a North Korea-Pakistan transfer would not have been news to the US allies, which have known of such transfers and viewed them as a business matter between sovereign states.

The Bush administration's approach, intended to isolate North Korea, instead left allies increasingly doubtful as they began to learn that the briefings omitted essential details about the transaction, US officials and foreign diplomats said in interviews. North Korea responded to public reports last month about the briefings by withdrawing from talks with its neighbors and the United States.

In an effort to repair the damage, Secretary of State Condoleezza Rice traveled through East Asia trying to get the six-nation talks back on track. She left Beijing, the last leg of her tour, Monday after going to Tokyo and Seoul earlier.

The new details follow a string of controversies concerning the Bush administration's use of intelligence on weapons of mass destruction. In the run-up to the Iraq invasion in March 2003, the White House offered a public case against Iraq that concealed dissent on nearly every element of intelligence and included interpretations unsupported by the evidence.

The United States briefed its allies on North Korea in late January and early last month. Shortly afterward, administration officials, speaking on condition of anonymity, said North Korea had sold uranium hexafluoride to Libya and portrayed the briefings as part of regular discussions with China, South Korea and Japan ahead of a new round of hoped-for negotiations on North Korea's nuclear program.

But in recent days the two other US officials said the briefings were hastily arranged after China and South Korea indicated they were considering bolting from the six-party talks. The talks have been seen as largely ineffectual, but the Bush administration, which refuses to meet bilaterally with Pyongyang, insists they are critical to curbing North Korea's nuclear program.

The White House declined to offer an official to comment by name about the new details concerning Pakistan.

A prepared response attributed to a senior administration official said the United States ``has provided allies with an accurate account of North Korea's nuclear proliferation activities.''

Although the briefings did not mention Pakistan by name, the official said they made it clear that the sale went through the illicit network operated by Pakistan's top nuclear scientist, Abdel Qadeer Khan. But the briefings gave no indication that US intelligence believes the material had been bought by Pakistan and transferred there from North Korea in a container owned by the Pakistani government.

They also gave no indication that the uranium was then shipped via a Pakistani company to Dubai in the United Arab Emirates and on to Libya. Those findings match assessments by the International Atomic Energy Agency, which is investigating Libya separately. Libya gave up its nuclear weapons program in December 2003.

Since Pakistan became a key US ally in the hunt for al-Qaeda leaders, the administration has not held President Pervez Musharraf accountable for actions taken by Khan while he was a member of Musharraf's cabinet and in charge of nuclear cooperation.

``The administration is giving Pakistan a free ride when they don't deserve it and hurting US interests at the same time,'' said Charles Pritchard, the Bush administration's special envoy for the North Korea talks until August 2003. ``As our allies get the full picture, it doesn't help our credibility with them,'' he said.

Pritchard, now a Brookings Institution fellow, and others had initially raised questions about the Libya connection when it became public last month. No one in the administration has been willing to discuss the uranium sale publicly.

CIA director Porter Goss spoke extensively about North Korea's nuclear arsenal and capabilities in testimony to Congress last month. But he gave no indication the intelligence community believed that North Korea had supplied nuclear materials to Libya, that it was capable of producing uranium hexafluoride, or that it was a member of the nuclear black market.

Two years ago, US officials told allies that North Korea was trying to assemble an enrichment facility that would turn uranium hexafluoride to bomb-grade material. But China and South Korea, in particular, have been skeptical and are becoming increasingly wary of pressuring North Korea.

The January and February briefings by senior National Security Council officials Michael Green and William Tobey were intended to do just that by keeping the spotlight solely on North Korea. Pakistan was mentioned only once in the briefing paper, and in a context that emphasized Pyongyang's guilt. ``Pakistani press reports have said the uranium came from North Korea,'' according to the briefing paper.

After initial press reports about the briefing appeared last month, Pyongyang announced that it possessed nuclear weapons and would not return to the six-party talks. Pritchard said North Korea's reaction was ``absolutely linked'' to the Green-Tobey trip.

The United States tried to persuade North Korea to return to the talks. It responded with a list of conditions, including a demand that Rice apologize for calling North Korea an ``outpost of tyranny.''

In Tokyo last week, Rice used softer language, telling a Tokyo audience that the US was open to negotiation and that North Korean leader Kim Jong Il should grab the opportunity.

THE WASHINGTON POST