The Justice Department is charging members of the Chinese military with conducting economic cyber-espionage against American companies, U.S. officials familiar with the case said Monday, marking the first time that the United States is leveling such criminal charges against a foreign country.

Attorney General Eric Holder is expected to make the announcement at a news conference Monday morning.

China’s Foreign Ministry did not immediately respond to requests for comment.

The indictment against members of the People’s Liberation Army follows vows by senior administration officials to hold other nations to account for computer theft of intellectual property from American industry.

China is widely seen as the nation that has been most aggressive in waging cyber-espionage against the United States.

The Justice Department said the news conference is scheduled for 10 a.m. Eastern time “to announce a criminal indictment in a national security case.” It said that in addition to Holder, the participants would be John Carlin, assistant attorney general for national security; David Hickton, the U.S. attorney for the Western District of Pennsylvania, based in Pittsburgh; and Robert Anderson, executive associate director of the FBI.

The charges are to be brought in western Pennsylvania, where several companies that were allegedly victimized are located. Authorities are expected to name the companies and the hackers, officials said.

In 2012, the Justice Department’s National Security Division began training hundreds of prosecutors to combat and prosecute cyber-espionage that poses a threat to national security. Later that year, Carlin, then principal deputy assistant attorney general, told Defense News that “you’ll see a case brought.”

Even if a prosecution never materializes, the indictment will send a powerful message that such acts will not be tolerated, officials said.

Estimates of the economic costs to the United States of commercial cyber-espionage range from $24 billion to $120 billion annually. China is by far the country that engages in the most such activity against the United States, according to a U.S. national intelligence estimate.

Senior U.S. officials have repeatedly warned China that its continued pilfering of intellectual property to benefit its industries will harm the two countries’ bilateral relationship.

In February 2013, the U.S. security firm Mandiant reported that it had linked a specific unit of the People’s Liberation Army to cyber-intrusions of more than 140 U.S. and foreign companies and entities.

The United States and China agreed last year to begin holding regular, high-level talks on cybersecurity and commercial espionage. But whenever U.S. officials raise the issue of economic spying, the Chinese are not receptive, administration officials said. Though Washington takes pains to distinguish between foreign intelligence gathering and spying to help a country’s own industries gain an economic advantage, officials say that is a distinction without a difference to the Chinese.

The leaks from former National Security Agency contractor Edward Snowden beginning last June have only complicated the talks. Beijing has pointed to disclosures by Snowden of vast NSA surveillance activities — including spying on Chinese companies — to assert that the United States is the greater aggressor in the area.