An inmate has pleaded guilty to murder in the stabbing death of a guard at a federal prison in Central California.

The U.S Attorney's Office says 48-year-old James Ninete Leon Guerrero, of Guam, entered the plea on Tuesday.

Prosecutors say Guerrero held Officer Jose Rivera down at the U.S. Penitentiary in Atwater in 2008 as another inmate, Jose Cabrera Sablan, stabbed him more than 20 times with an eight-inch shank. The 22-year-old Rivera - a U.S. Navy veteran - was doing a daily headcount when he was attacked.

Guerrero was serving a life prison sentence at the time in connection with an armed bank robbery. Prosecutors say under a plea agreement, he will receive another life term. Sablan is scheduled to go on trial in April.