Two former CIA contractors who designed the harsh interrogation program used after the Sept. 11 attacks are being summoned to testify before the military tribunal at the Guantanamo Bay, Cuba, detention center.

The government has approved a defense request to have James Mitchell and Bruce Jessen testify in the case against five men charged with helping to plan and assist the 2001 attacks.

The two psychologists are among a dozen approved witnesses listed in a letter sent Monday to the defense. They have never testified in public.

Mitchell and Jessen designed and implemented an interrogation program that included such abusive techniques as prolonged sleep deprivation, confinement in small, enclosed spaces and waterboarding.

They could testify as early as July in a pretrial hearing at the U.S. base.