The US Justice Department has announced that an American tour guide has been charged with spying for China's intelligence services.
Xuehua Peng delivered classified information to China's Ministry of State Security (MSS), the BBC quoted prosecutors as saying on Monday.
Mr Peng, 56, allegedly completed five "dead drops" at hotel rooms between 2015 and 2018.
Dead drops are used by spies to pass information or items in secret locations.
He was arrested on September 27 in Hayward, California, and denied bail at a court hearing.
"The conduct charged in this case alleges a combination of age-old spy-craft and modern technology," US Attorney David Anderson said.
The FBI snared Mr Peng as part of an elaborate "double agent operation" launched in March 2015.
A "confidential human source" - an FBI double agent - passed national security secrets to Mr Peng in return for payment, the prosecutors added.
Covert FBI footage, released by the Justice Department, showed Mr Peng conducting some of the dead drops, the prosecutors said.
Mr Peng's arrest "exposes and disrupts an operation by those Chinese intelligence officers to collect such information without having to step foot in this country", Assistant Attorney General of National Security John Demers said.
Trained in traditional Chinese medicine, Mr Peng is believed to have been working as a sightseeing tour operator in the San Francisco area for Chinese students and visitors.
He is expected to appear in court for a detention hearing in San Francisco on Wednesday. If convicted of the charges, he faces a maximum sentence of 10 years, and a fine of $250,000.