Investigators have identified China as the origin of some nuclear weapons designs found in Libya last year, the Washington Post newspaper reported.
Gaddafi's move was hailed around the world
It said the international inquiry found that Chinese designs probably supplied to Pakistan in the 1980s were sold on to Libya by Pakistani-led smugglers.
It quoted officials as saying that some of Libya's documents were in Chinese.
The findings raise questions as to whether similar Chinese designs were supplied to Iran and North Korea.
Former UN arms inspector David Albright was quoted by the Washington Post as saying that Libya did not have a suitable missile to carry the weapon featured in the designs, but Iran and North Korea had more advanced rocket programmes.
Mr Albright later told the BBC's World Today programme that experts thought similar information "was offered to Iraq in 1990 - and Iraq just did not have a chance to pursue that deal because it was right before the Persian Gulf war started in January 1991".
"You have to almost conclude it went to Iran and... North Korea," Mr Albright said.
There has been no official reaction to the newspaper's report from China, which has long been thought to have provided Pakistan with nuclear technology until the 1980s.
The inquiry was launched after Libya's leader Colonel Gaddafi had decided to abandon the pursuit of the weapons of mass destruction and handed over the country's nuclear secrets to the US.
The blueprints had been analysed by experts from the US, Britain and the Vienna-based International Atomic Energy Agency, the newspaper said.
Last month, the "father" of Pakistan's nuclear bomb, Dr Abdul Qadeer Khan, publicly admitted supplying nuclear technology to North Korea, Iran and Libya through a black market.
Government officials and arms experts said Libya's documents yielded "dramatic evidence" of China's long-suspected role in the transfers of nuclear know-how to Pakistan, according to the newspaper.
Pakistan began its nuclear programme in the 1970s
It said the packet of documents contained detailed, step-by-step instructions for assembling an implosion-type 450-kilogram (1,000 pounds) nuclear bomb that could fit atop a large ballistic missiles.
They also included technical instructions for manufacturing components of the device, the officials and experts were quoted as saying.
"It was just what you'd have on the factory floor. It tells you what torque to use on the bolts and what glue to use on the parts," one arms expert who had reviewed the designs told the newspaper.
He described the blueprints as "very, very old" but "very well engineered".
China's actions "were irresponsible and short-sighted, and raise questions about what else China provided to Pakistan's nuclear programme," Mr Albright told the Washington Post.
The newspaper quoted an official familiar with the documents as saying the device depicted in the blueprints appeared similar to a weapon tested by China in the 1960s.
Pakistan successfully tested its first nuclear bomb in 1998, but it was a more modern design than the one sold to Libya, Mr Albright told the newspaper.
He said the Libyan documents "do not appear to contain any information about the nuclear weapons Pakistan has built".