In January 2002, Chinese officials said that they had discovered that China's presidential aircraft had been bugged after it was refurbished in the United States. The Chinese said that they had found 27 listening devices on board, including some in the bathroom and in the headboard of the Chinese president's bed. China bought the airplane in June 2000 for $120 million, and it was sent to San Antonio International Airport for refitting by several contractors. It was delivered to the Chinese government in August 2001.

The Chinese said that they had discovered the listening devices in October 2001, soon after accepting delivery on the plane.

Law enforcement officials today played down the possibility of a connection between the F.B.I. case and the airplane operation, and said that senior F.B.I. officials were not certain that a link would be found.

Yet officials said they were still in the beginning phases of their investigation of the F.B.I. case, and so it will take more time to determine the full extent of any damage to national security. The F.B.I. and the Justice Department are conducting separate investigations into the case, as investigators examine what secrets Ms. Leung may have given up and what management problems at the F.B.I. may have allowed the problem to go undetected.

''We have to look at everything,'' a senior law enforcement official said today. ''No conclusions have been reached. We'll have to go through a whole assessment of what she knew.''

Still, F.B.I. officials are skeptical of what Mr. Smith has told them. Prosecutors noted in court filings last week that Mr. Smith denied having an affair with Ms. Leung, only to be contradicted by tapes that recorded the pair in a hotel.

Mr. Smith was Ms. Leung's F.B.I. handler for nearly 20 years, and the two had an affair for almost as long, court documents said. Ms. Leung was a highly paid F.B.I. informer, but prosecutors now say that she took classified documents from Mr. Smith, photocopied them, and passed them to handlers in Beijing.