China has stolen or acquired top secret information on every US-deployed nuclear missile and this espionage is almost certainly continuing, according to an official report which will further damage relations between the two countries.
The report comes as the US is trying to repair diplomatic ties with China, which are badly strained over the bombing of the Chinese embassy in Belgrade. The timing of the report may also affect the US attitude to China's efforts to join the World Trade Organisation.
The extent of Chinese access to US nuclear weapon technology over the past 20 years has shocked politicians from all sides and has led to calls from Republicans for the resignation of President Clinton's National Security Advisor, Mr Sandy Berger, and the Attorney-General, Ms Janet Reno.
Ms Reno is criticised for refusing to allow the FBI to put a wiretap on a Chinese-American scientist who has since been dismissed for alleged spying but not charged.
Mr Clinton is facing criticism for denying any knowledge of Chinese espionage at the nuclear laboratories during his presidency when questioned at a press conference last March. But the report says he was briefed about leaks by Mr Berger in 1997 and received the present damaging report last January.
The White House, which is braced for an onslaught from Congress, says that the espionage began 20 years ago but it was Mr Clinton who took the first steps to tighten up security at the nuclear laboratories.
Mr Clinton also appointed a new Secretary of Energy, Mr Bill Richardson, who claimed yesterday to have "plugged leaks" at the nuclear laboratories. He said that the administration would now implement the report's 38 recommendations.
The report by a select congressional committee, chaired by a Republican Congressman, Mr Christopher Cox, was completed at the end of last year but has been released only after months of wrangling with the White House, which wanted it to remain secret. About one-third of the 700-page report has been withheld for security reasons
Congressman Norm Dicks, the senior Democrat on the committee, said the report documented "one of the worst counter-intelligence failures in the nation's history". But he also said that China did not seem to have deployed any warheads using the technology it is alleged to have stolen.
Mr Cox's bipartisan committee was originally asked to investigate the unauthorised transfer of missile technology to China by US corporations such as Loral Space and Communications and Hughes Electronics, which use Chinese missiles to launch their satellites. But the scope of the inquiry was soon widened to include suspected Chinese espionage at nuclear laboratories such as Los Alamos, where the atomic and hydrogen bombs were developed.
Some members of Congress are comparing Chinese theft of nuclear secrets to the Soviet Union's espionage in the 1940s, which led to it acquiring atomic weapons much sooner than expected.
Information on seven US nuclear warheads, including the most advanced on the Trident missile used on nuclear submarines, is believed to have been obtained by China in the 1980s but this was not discovered until 1995, apparently through a Chinese defector. The report also refers to the apparent theft of "neutron" bomb technology in 1995 but says this is still under investigation.
In the late 1990s China obtained "electromagnetic weapons technology" that could be used to attack satellites and missiles, improved detection techniques that could be used against submarines, and obtained "research technology that if taken to successful conclusion could be used to attack US satellites and submarines".