Washington  - Ali al-Marri, an alleged "al-Qaeda sleeper" accused of facilitating terrorist attacks on the United States, has entered a surprise guilty plea to a conspiracy charge, the US-based television network CNN reported late Thursday, quoting the US Justice Department.

   Al-Marri, who was the centre of controversy over the status of alleged "enemy combatants" on US soil in the wake of the September 11, 2001 terrorist attacks, had been accused of helping al-Qaeda terrorists enter the country.

   "Ali al-Marri was an al-Qaeda 'sleeper' operative working on US soil and directed by the chief planner of the 9/11 attacks," the network quoted Arthur Cummings, executive assistant director of the FBI's National Security Branch, as saying in a Department of Justice statement.

   The Qatar native, who was a student at Bradley University in Peoria, Illinois when he was arrested in 2001, entered his surprise guilty plea during a two-hour hearing in a federal courtroom in Peoria.

   Al-Marri admitted he "knowingly conspired" with a known terrorist.

   He is scheduled to be sentenced July 30. Under the terms of a plea bargain, he will face a sentence of up to 15 years in jail.