WASHINGTON (CNN) -- A Defense Department weapons system analyst and three Chinese nationals have been arrested and charged in two espionage-related cases, prompting a top Justice Department official Monday to declare Chinese espionage is approaching "Cold War levels."
In a case brought by federal prosecutors in Virginia, a civilian analyst for the Defense Security Cooperation Agency stands accused of selling to two Chinese associates classified information detailing U.S. weapons sales to Taiwan.
In a separate case, California prosecutors arrested and charged a long-time employee and contractor for Boeing and Rockwell with providing Beijing secrets dealing with the space shuttle and several other sensitive military aircraft and rocket programs.
Assistant Attorney General Kenneth Wainstein, in a news conference announcing the arrests and charges, twice cited congressional testimony that concluded "aggressive" Chinese government espionage programs have reached levels not seen since the Cold War with the former Soviet Union.
"It's a threat to our national security and to our economic position in the world, a threat that is posed by the relentless efforts of foreign intelligence services to penetrate our security systems and steal our most sensitive military technology and information," Wainstein said. Watch authorities discuss the two cases »
Wainstein said the Chinese government is among the most aggressive of foreign powers seeking access to U.S. military and economic secrets.
In the Virginia case officials charge that Gregg Bergersen, 51, of Alexandria, Virginia, sold highly classified information to Tai Shen Kuo, 58, a naturalized citizen who resides in New Orleans, Louisiana. Kuo then allegedly handed the information to Yu Xin Kang, 33, a lawful resident alien also living in New Orleans. Kang in turn allegedly gave the information to a spy for the Chinese government.
Kang, a permanent U.S. resident, will make her initial appearance Monday in a federal court in New Orleans before she is transferred to Virginia to stand trial.
Bergersen and Kuo made initial court appearances in Alexandria, but because they had no lawyers were ordered detained pending a detention hearing Thursday. Bergersen, who was arrested Monday morning, was still wearing a T-shirt and shorts as he appeared before a magistrate judge.
A woman identifying herself as Bergersen's wife told reporters her husband is innocent and the charges had "come out of the blue."
At the Washington news conference, officials declined to comment on how much Bergersen was paid, or whether he knew the destination of the secrets he sold.
Justice Department officials said Kuo cultivated friendships with Bergersen and others at the direction of an unidentified official of the Beijing government. Kuo allegedly "gathered national defense information on behalf of the government" of China from January 2006 to this month.
Meanwhile, in Santa Ana, California, a long-time defense industry employee and contractor was scheduled to appear in court for allegedly providing military secrets to Beijing. Watch where the U.S. says Chinese spies are working »
"A document says he did it out of loyalty to the Motherland," said U.S. Attorney Thomas O'Brien.
O'Brien said Dongfan "Greg" Chung, 72, of Orange, California, a naturalized U.S. citizen, had worked for Rockwell, Boeing and a Boeing contractor for more than 30 years.
"Chung made multiple trips to the PRC [People's Republic of China] to deliver lectures on technology involving the space shuttle and other programs, and during those trips he met with officials and agents of the PRC government," O'Brien said. Chung also allegedly provided information on the C-17 military transport and the Delta IV rocket.
He is scheduled to appear before a federal magistrate in Santa Ana, California, late Monday, officials said.
Prosecutors say the case is linked to that of another engineer, Chi Mak, who was convicted last year along with several family members of providing information to the Beijing government. E-mail to a friend
CNN's Kevin Bohn contributed to this report.