U.S. Secretary of Defense Robert Gates has ordered his staff to prepare a plan to shut down the prison at the U.S. naval base in Guantanamo Bay, Cuba, the Pentagon said Thursday.

Pentagon spokesman Geoff Morrell said Gates' instructions are based on President-elect Barack Obama's declaration that closing Guantanamo is a priority.

Obama has asked Gates, who took office two years ago, to remain on his post.

The plan will deal with issues such as how to close the prison and where to move the detainees, including alleged 9/11 mastermind Khalid Sheikh Mohammed, he added.

The United States opened the Guantanamo prison in January 2002 to hold terror suspects and Taliban members mainly captured during the U.S.-led war in Afghanistan. About 250 prisoners are being held there.

The international community and human rights groups have been constantly calling for its closure.