The professor, Reese Roth, is a plasma scientist who was was hired to work on a US Air Force research contract by privately held firm, Atmospheric Glow Technologies Inc, of Knoxville, Tennessee.

The company pleaded guilty last month to illegally providing a Chinese national, Xin Dai, with data used in developing an unmanned aerial weapons system. Xin Dai was Roth's research assistant.

Another former Atmospheric Glow employee, Daniel Sherman, pleaded guilty in April to charges of conspiring with Roth to export the data.

Roth, 70, maintained that he did not break the law, but a jury in Knoxville found him guilty on 17 counts of conspiracy, fraud and violating the Arms Export Control Act, the Justice Department said.

'Today's guilty verdict should serve as a warning to anyone who knowingly discloses restricted U.S. military data to foreign nationals,' Mr Patrick Rowan, acting assistant attorney general for national security, said in a statement.

'The illegal export of such sensitive data represents a very real threat to our national security, particularly when we know that foreign governments are actively seeking this information for their military development.'

Roth is scheduled for sentencing in January. He was accused of passing information to Xin Dai and of carrying documents containing data about unmanned aerial systems to China without an export license.

US intelligence services in recent years have accused China of increasing spying operations in the United States to collect military and economic secrets.

A former Boeing engineer, charged in February with stealing space shuttle secrets for China, pleaded guilty in July to unauthorised possession of defence information.

China has denied spying allegations and says such charges are an example of Cold War thinking. -- REUTERS