A defense contractor pleaded guilty Thursday to giving military secrets to his Chinese girlfriend and faces up to 20 years in prison when he is sentenced this summer.

Benjamin Bishop, 60, told U.S. District Magistrate Judge Kevin Chang that he "spoke too much" in an email and brought classified documents to his home. Bishop was a lieutenant colonel in the U.S. Army Reserve.

Wearing a white jumpsuit and chains, Bishop pleaded guilty to communicating national defense information to a person not entitled to receive it and willful retention of national defense information.

His attorney, Birney Bervar, said the case was about love, not espionage, and that Bishop was only trying to help his girlfriend with an assignment. He was arrested last March at the U.S. Pacific Command headquarters, where he worked.

Bishop will be sentenced by U.S. District Judge Leslie Kobayashi on June 26. He faces up to 10 years in prison and a $250,000 fine for each count. He was returned to the Federal Detention Center.