WASHINGTON (CNN) -- A Pentagon official has been charged with leaking classified information to a business client who was taking orders from China's government, the Justice Department said Wednesday.

James Wilbur Fondren Jr., 62, is accused of "conspiracy to communicate classified information to an agent of a foreign government" from November 2004 until February 2008, department officials said in a written statement.

Fondren, who began working as a civilian deputy director for the Washington liaison office for U.S. Pacific Command in 2001 and has been on administrative leave with pay since mid-February of last year, turned himself in to federal agents Wednesday morning.

"The allegations in this case are troubling -- providing classified information to a foreign agent of the People's Republic of China is a real and serious threat to our national security," said Dana Boente, acting U.S. attorney for the Eastern District of Virginia.

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An unsealed criminal complaint revealed the course of the FBI's investigation of Fondren.

Fondren, a retired Air Force colonel, began providing private consulting services from his Virginia home in February 1998, according to an affidavit from FBI special agent Robert Gibbs. His sole client was a friend, Tai Shen Kuo, a naturalized U.S. citizen from Taiwan who maintained business interests in the United States and China, according to the affidavit.

Fondren went to work three years later in the U.S. Pacific Command's Washington liaison office, where he had top security clearance, Gibbs said.

The FBI's investigation revealed that even after taking the Pentagon job, Fondren continued to provide consulting services to Kuo, who, unbeknownst to Fondren, was paid by the Chinese government to collect information, according to the affidavit.

At one point, the affidavit says, Kuo told Fondren that he was providing information to the government of Taiwan, Gibbs said.

Fondren incorporated Defense Department documents and other classified information into e-mailed "opinion papers" that he sold to Kuo for between $350 and $800 each, Gibbs said.

Kuo was arrested in February 2008 when he was staying at Fondren's Virginia home, according to the affidavit. At the time, Kuo possessed a draft unclassified copy of a document called "The National Military Strategy of the United States of America 2008."

Fondren later admitted to the FBI that he gave the copy to Kuo, Gibbs said.

Another Pentagon official, Gregg William Bergersen, was arrested the same day as Kuo and was accused of providing Kuo with government information, the affidavit said. Kuo's dealings with Bergersen were separate from his alleged dealings with Fondren, Gibbs said.

Bergersen pleaded guilty to a charge of conspiracy to disclose defense information and was sentenced to four years and nine months in prison, the Justice Department said in a news release.

Kuo admitted he had obtained national defense information from Bergersen and was sentenced to a prison term of 15 years and eight months, the department said.

Yu Xin Kang, a Chinese citizen living in New Orleans, Louisiana, who was arrested on the same day as Kuo and Bergersen, admitted she helped Kuo pass information to the Chinese government and was sentenced to 18 months in prison, the department said.

"Espionage is a profoundly serious crime, and the FBI will continue to work with our law enforcement and intelligence community partners to ensure the protection of our nation's most sensitive information," said Arthur Cummings of the FBI's National Security Branch.

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