Washington: In a disclosure likely to embarrass Beijing on the eve of President Barack Obama's visit, a leading US daily Friday reported that China gifted 50 kg of uranium to Pakistan with a do-it-yourself kit to make two atomic bombs in 1982.

Citing accounts by controversial Pakistani scientist A.Q. Khan, The Washington Post said enough weapons-grade uranium for two atomic bombs was transferred to Pakistan in five stainless-steel boxes loaded on a Pakistani military C-130 aircraft from the western Chinese city of Urumqi.

The uranium transfer was part of a broad-ranging, secret nuclear deal approved years earlier by Mao Zedong and Pakistan Prime Minister Zulfiqar Ali Bhutto, according to the accounts by Khan, the father of Pakistan's nuclear weapons programme, who is under house arrest in Pakistan, the daily said.

According to Khan's account, "provided to The Washington Post", the uranium cargo came with a blueprint for a simple weapon that China had already tested, supplying a virtual do-it-yourself kit that significantly speeded Pakistan's bomb effort.

The transfer also started a chain of proliferation, the Post noted with US officials worrying that Khan later shared related Chinese design information with Iran; in 2003, Libya confirmed obtaining it from Khan's clandestine network.

"Upon my personal request, the Chinese Minister . . . had gifted us 50 kg of weapon-grade enriched uranium, enough for two weapons," Khan wrote in a previously undisclosed 11-page narrative of the Pakistani bomb programme that he prepared after his January 2004 detention for unauthorised nuclear commerce.

"The Chinese gave us drawings of the nuclear weapon, gave us 50 kg enriched uranium," he said in a separate account sent to his wife several months earlier.

The influential US daily cited unnamed US officials as saying they have known about the transfer for decades and once privately confronted the Chinese - who denied it - but have never raised the issue in public or sought to impose direct sanctions on China for it.

President Obama, who said in April that "the world must stand together to prevent the spread of these weapons," plans to discuss nuclear proliferation issues while visiting Beijing Tuesday.

Although Chinese officials have for a quarter century denied helping any nation attain a nuclear capability, current and former US officials cited by the Post say Khan's accounts confirm the US intelligence community's long-held conclusion that China provided such assistance.