Underwood, a former contract civilian guard, pleaded guilty in U.S. District Court in Washington to one count of attempting to communicate national defense information to a foreign government, the article reports.

Sentencing guidelines normally mean a prison sentence of 15 to 20 years, and sentencing is set for November 19.

Among materials Underwood attempted to sell to the Ministry of State Security, China's main counter-intelligence agency, were classified pictures and diagrams of the security measures and devices being installed in the new building, Reuters reports.

A U.S. official said the materials might have enabled Chinese intelligence to install electronic surveillance gear in the building before U.S. officials moved in, according to the article. Underwood also told U.S. investigators he had put together a plan for Chinese agents to get access to a consulate building to install listening and other devices.

He was arrested on the run by FBI agents in Los Angeles in September 2011 after initial charges that he lied about why he was taking photos of the consulate, the article reports.

Underwood, a former Indiana resident, had worked as a guard at the consulate construction site from November 2009 to August 2011. He planned to sell the information after he was hit by stock market reverses, the statement said, the article says.

U.S. prosecutors have brought charges against numerous people over the years for trying to spy for China, including some who sought money in exchange for economic or national security-related information, Reuters reports.