Petty Officer Wenheng "Thomas" Zhao, 26, pleaded guilty last October to conspiracy and receiving a bribe. Zhao, who had faced a maximum of 20 years in prison, was also fined $5,500, the U.S. justice department said in a statement.

Zhao, who worked at Naval Base Ventura County in California, admitted sending his Chinese handler plans for U.S. military exercises in the Indo-Pacific region, operational orders, and electrical diagrams and blueprints for a radar system on a U.S. military base in Okinawa, Japan.

"Zhao chose to betray the oath he took to our country and put others at risk," said Larissa Knapp, executive assistant director of the Federal Bureau of Investigation's National Security Branch.

"Today's sentencing demonstrates, yet again, the inability of China's intelligence services to prevent the FBI and our vital partners from apprehending and prosecuting the spies China recruits," she said in a statement.

The United States has accused China of an extensive campaign of espionage and cyberattacks, a charge that Beijing rejects.

(Reporting by David Ljunggren; Editing by Caitlin Webber and Bill Berkrot)