US-China relations are becoming strained over the accusations that Beijing has stolen top secret US information to develop its nuclear weapons.
The US Secretary of Energy, Mr Bill Richardson, who dismissed a Chinese-American scientist this week for alleged spying at the Los Alamos laboratories, said yesterday: "We are concerned that the Chinese are conducting espionage. . . we make no illusions about Chinese behaviour".
Mr Richardson said that the scientist, who has been named in the media as Mr Wen Ho Lee, was dismissed because "he had misused security, he had improper contact with foreign officials and violated a number of security procedures". "But clearly we don't know the extent of the damage from these thefts. They were serious," Mr Richardson said.
Mr Lee has been under investigation as a suspect for several years but has not yet been charged with any offence. The FBI has had difficulties in gathering evidence against him over the spying accusations, which go back to the mid-1980s, when it is believed China obtained information from Los Alamos which helped it to develop a miniaturised nuclear device.
Another Los Alamos Chinese-American scientist, Mr Peter Lee, recently served a 12-month sentence for handing over information on national security laser programmes during a trip to China in 1985.
Republican leaders are now accusing the Clinton administration of failing to take proper security precautions to protect its nuclear secrets after it was given evidence of Chinese espionage in 1997. Critics say that the White House played down security concerns at a time when President Clinton was eager to improve diplomatic and trade relations with China.
It is also pointed out that, under President Clinton, controls on the sale to China of nuclear and satellite technology for civilian purposes were relaxed, allowing US firms to negotiate lucrative contracts.
Shortly before Mr Clinton was re-elected in November 1996, there were charges that the Chinese government was channelling money into the Democratic election campaign. A Senate investigation in 1997 into these and other charges of foreign interference in the election was inconclusive.
The Senate Intelligence Committee now plans to hold secret hearings later this month on nuclear security lapses.
Vice President Al Gore said yesterday China's alleged theft of nuclear secrets happened during a "previous administration" and President Clinton's government had acted to fix the problem.