Beijing has strongly rejected the United States' latest espionage allegations, denouncing the claims as 'farces' that should come to an end.
'The so-called accusations against China are totally fictitious and have ulterior motives,' Foreign Ministry spokesman Liu Jianchao said yesterday. 'I think everyone is weary of these farces, and they should end.'
US authorities arrested four men on Monday on espionage charges related to the sale of military and commercial secrets to the mainland.
Former Boeing engineer Dongfan 'Greg' Chung, 72, a naturalised US citizen, allegedly stole trade secrets about several aerospace programmes, including the Space Shuttle, and sold them to the mainland.
Individuals in the Chinese aviation industry began sending Chung letters asking for specific information as early as 1979, and Chung responded in a letter indicating his desire to help the 'motherland', according to the US Justice Department.
In a separate case, Pentagon weapons systems policy analyst Gregg William Bergersen allegedly sold information to a Chinese furniture salesman outlining every planned US sale of weapons or other military technological advancements to Taiwan in the next five years.
The salesman, Tai Shen Kuo, a 58-year-old naturalised US citizen, then forwarded the information to Beijing through middleman Kang Yuxin, a 33-year-old Chinese national who is a US resident.
The whole operation spanned January 2006 to February this year.
On Tuesday, assistant US Attorney General Kenneth Wainstein described the spying activities as 'a threat to our national security and to our economic position in the world', and said the mainland's spying efforts were approaching 'cold war levels'.
He said that the mainland was one of the countries 'particularly determined and methodical in their espionage efforts', and that charges had been pressed in a half-dozen espionage cases in the past six months in relation to such efforts.
Mr Liu denied the mainland was conducting espionage, saying the allegations were 'irresponsible' and did no good to Sino-US relations.
'We demand the US stop its cold war thinking and stop making groundless accusations and do more to contribute to our mutual trust and the friendship between our two peoples,' he said.