U.S. officials said the intelligence community has concluded that North Korea and Pakistan cooperated to provide material for Libya'snuclear weapons program.

"We do have evidence that what arrived in Libya was actually of North Korean origin," Christopher Hill, the leading U.S. negotiator on North Korea's nuclear program, said. "We believe that it was brokered through Pakistan, with knowledge that it would end up in Libya."

Hill has ended his current post as U.S. ambassador to South Korea. Over the weekend, he arrived in Washington to serve as assistant secretary of state for East Asian affairs, Middle East Newsline reported.

Officials said the Pakistani smuggling network of Abdul Qadir Khan was aided by the two countries in arranging the sale and delivery of uranium hexafluoride, a key element in the enrichment of uranium.

In February 2004, the Bush administration informed U.S. allies in Asia that North Korea exported uranium hexafluoride, or UF6, to Libya. Officials said the UF6 shipment was brokered through Pakistan in an effort by Pyongyang to obtain hard currency.

In a seminar sponsored by the Civil Network for a Peaceful Korea, Hill departed from the Bush administration's policy of distancing Pakistan from any involvement in nuclear proliferation. Hill said North Korea exported uranium hexafluoride through the Khan network with knowledge that the material would arrive in Libya. Pakistan and North Korea have been regarded as strategic allies and cooperate on missile and nuclear issues.

Officials said the intelligence community has not determined that Pakistani President Pervez Musharraf was personally involved in the Khan network. But they said Musharraf's refusal to allow the CIA to question Khan has raised concerns that he received support from the highest levels of the Pakistani government.

"No one is saying that government of Pakistan was involved," Hill told the seminar on April 6. "But they are saying that a well known international broker of nuclear materials [Khan] brought it to Libya from North Korea."

At the seminar, Hill said North Korea has supplied uranium to Libya for its nuclear weapons program. He said the equipment was meant for the enrichment of uranium.

"They have been making purchases of very, very specialized — and I might add, extremely expensive — equipment whose purpose one has to believe is to have an HEU program," Hill said. "A lot of the information about this has come to light as the result of breaking of the A.Q. Khan network."