A former Central Intelligence Agency officer who was paid hundreds of thousands to leak United States defence and intelligence secrets, has pleaded guilty to spying for China, the US Justice Department said.

Key points: Lee left the CIA in 2007 and became a resident in Hong Kong

Lee left the CIA in 2007 and became a resident in Hong Kong He allegedly wrote handwritten notes about intelligence by CIA assets

He allegedly wrote handwritten notes about intelligence by CIA assets He faces a maximum penalty of life in prison

Jerry Chun Shing Lee was approached in 2010 by two Chinese intelligence officers who offered to pay him $US100,000 ($143,800) and to take care of him "for life" for information he had acquired as a CIA officer, according to a US Justice Department statement.

The now 54-year-old left the CIA in 2007 and had moved to Hong Kong.

Hundreds of thousands of dollars were subsequently paid into Lee's personal bank account between 2010 and 2013, according to the statement.

The statement also said that Lee created thumb drives containing secret information about CIA activities and the location and time frame of a sensitive operation.

An FBI search in 2012 of a Honolulu hotel room registered to Lee also discovered handwritten notes by him about his work as a CIA officer before 2004.

"These notes included, among other things, intelligence provided by CIA assets, true names of assets, operational meeting locations and phone numbers, and information about covert facilities," the statement said.

'A tragic betrayal'

US Assistant Attorney General for National Security John Demers said, it was the third case in less than a year in which a former US intelligence officer had pleaded guilty or been found guilty of conspiring to pass defence secrets to China.

"Every one of these cases is a tragic betrayal of country and colleagues," he said in the statement.

Lee's sentencing is set for August 23 and he faces a maximum penalty of life in prison.

Lee's case is the third in less than a year where a US intelligence officer has been found to conspire with China. ( ABC News: Nic MacBean )

Neither Chinese officials nor Lee's attorney were immediately available to comment after normal business hours.

In March, a former US Defence Intelligence Agency officer, Ron Rockwell Hansen, pleaded guilty to attempting to transmit classified information to China and receiving hundreds of thousands of dollars while acting as an agent for Beijing.

Last June, another former CIA case officer, Kevin Mallory, was convicted on espionage charges for passing classified documents to China.

This week, FBI Director Christopher Wray said China posed the biggest threat to the United States when it came to economic espionage.

Reuters