The U.S. Cyber Command’s top intelligence officer accused China on Thursday of persistent efforts to pierce Pentagon computer networks and said a proposal was moving forward to boost the cyber command in the U.S. military hierarchy.

“Their level of effort against the Department of Defense is constant” while alleged Chinese attempts to steal corporate trade secrets has been growing, Rear Admiral Samuel Cox, the command’s director of intelligence, told Reuters after remarks to a forum on the history of cyber threats.

The Office of the National Counterintelligence Executive, a U.S. intelligence arm, said in a landmark report a year ago that “Chinese actors are the world’s most persistent perpetrators of economic espionage.”

“It’s continuing apace,” Cox said. “In fact, I’d say it’s still accelerating.” He accused China of trying to “exfiltrate” Pentagon secrets, jargon for sneaking them out.

Asked whether any classified U.S. networks had been successfully penetrated -- something not publicly known to have occurred -- Cox replied: “I can’t really get into that.”

A spokesman for the Chinese embassy did not immediately respond to a request for comment. In the past Chinese officials have denied such accusations.

Cyber Command is responsible for defending Defense Department networks as well as mounting any U.S. offensive operations in cyberspace. It was created about two years ago as a unit of the U.S. Strategic Command, the outfit responsible for U.S. nuclear and space operations.

Cox said a proposal was moving forward to elevate the cyberwarfare unit to the status of a full unified combatant command. This would put it on the same footing as its parent Strategic Command and the Defense Department’s eight other top-level military units.