Most of the 971 so called "suspicious contact reports" from US defense contractors and security and counterintelligence staff in 2005 were linked to the East Asian region, said the study, a copy of which was obtained by AFP.

Prepared by the Defense Security Service Counterintelligence Office, the unclassified document said "the majority of reported targeting originated from East Asia and the Pacific, which accounted for 31 percent of all reporting.

"The apparent across-the-board surge in activity from East Asia and Pacific countries will continue in the short term as gaps in technological capability become apparent in their weapons development processes," it said.

A total of 106 countries were linked in the report to "suspicious activities" pertaining to secret military technology in 2005, up from 90 countries a year earlier, the report said. The Middle East emerged second after East Asia with 23.1 percent of the cases, followed by Eurasia with 19.3 percent and South Asia with 13.2 percent.

In one case, a foreign" woman "seduced" an American male translator to give her his password in order to log on to his unclassified network, the report said, without giving particulars. "Upon discovery of this security breach, a computer audit revealed foreign intelligence service viruses throughout the system, it said.

The study did not identify countries.

"Identifying particular countries will make it a classified document," a spokeswoman for the Defense Security Service told AFP.

The report said however that lasers and optics technology and aeronautics appeared to be "priority technology targets" for the East Asian region. South Asia was more keen on obtaining secrets pertaining to signature control technology.

After terrorism, the greatest threat to US national security at home is espionage, officials say.

Many American state agencies have cited China as the top counterintelligence threat, with as many as 3,500 Chinese "front companies" reportedly gathering intelligence, especially highly-prized information technology.

Just last month, a Chinese national was charged in California with stealing military trade secrets and using them in demonstration and sales proposals to Beijing as well as the air forces of Malaysia and Thailand.

Xiaodong Sheldon Meng, 42, allegedly stole military combat and commercial simulation software and other materials from his ex-employer Quantum3D, a San Jose-based company.

Meng, a resident of Cupertino in California and facing 36 "economic espionage" charges, was said to have stolen trade secrets from Quantum3D "with the intent that they would be used to benefit the foreign governments of China, Thailand, and Malaysia."

"The alleged economic espionage and theft and export of trade secrets such as these -- visual simulation training software that has military application, no less -- has real consequences that could jeopardize our country's military advantages in the world," said US attorney Kevin Ryan.

The US Office of the National Counterintelligence Executive in an annual report to Congress in August last year underlined the challenge of protecting sensitive US technologies from foreign theft, citing globalization and the openness of the US economy to both trade and labor flows.

While the FBI had expanded its counterintelligence cooperation with key defense contractors, that may not be enough, said Peter Brookes, a former senior Pentagon official.

"We've clearly got to do more to prevent foreign spies from nicking sensitive American information for ill-gotten commercial, military -- or worse yet -- terrorist gain," he said.

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