WASHINGTON, March 13: Information obtained from accused Pakistani nuclear scientist Dr Abdul Qadeer Khan suggests North Korea began to pursue a highly enriched uranium programme for nuclear weapons several years earlier than originally thought , US officials said on Friday.

The officials, interviewed by Reuters, cited this disclosure as evidence that Pakistan has been cooperative in sharing with Washington the secrets of Dr Khan's global network that sold nuclear technology to Iran, North Korea and Libya.

US allegations about an HEU programme are central to six-party talks on North Korea's nuclear programme and US officials said they have used Dr Khan's information to buttress their case with their negotiating partners.

But officials also said that five weeks after Dr Khan confessed his deeds, the United States still has not had direct access to the disgraced scientist, who is known as the father of Pakistan's nuclear programme.

Dr Khan presumably could provide concrete answers to many key questions, including whether he sold nuclear weapon designs to Iran, which says its programme is only peaceful.

Some US sources said the Bush administration was unhappy with Pakistan's cooperation but a senior US official said these reports are "highly exaggerated."

Asked if Islamabad's cooperation was sufficient, the senior official replied: "I think, we think it is an ongoing process."

"We get regular briefings from the Pakistanis about what they are finding out and have been able to share this with other partners in the six-party talks" on the North's nuclear programme, he said.

But a second senior official said: "We don't know what Khan has ... We've been told that it's coming."

"The Pakistanis are going to give us what they feel like giving us," a third US source said.

Secretary of State Colin Powell is due to visit Pakistan as part of a South Asia trip next week and he is expected to discuss Dr Khan and related proliferation issues with President Pervez Musharraf and other officials.-Reuters