FACTBOX: Details about the US prison at Guantanamo Bay, Cuba

(Reuters) - President Barack Obama on Thursday discussed his plan for closing the U.S. military prison at Guantanamo Bay, Cuba, in an effort to stop a revolt by lawmakers concerned that some of the detainees could be set free in the United States.

Here are some facts about the prison camp at the U.S. naval base in Cuba.

WHY WAS IT SET UP?

* The detention camp was set up by the Bush administration in 2002 to hold foreigners captured after U.S.-led forces invaded Afghanistan to root out al Qaeda and its Taliban protectors in response to the attacks of September 11, 2001, that killed nearly 3,000 people in New York, Washington and Pennsylvania.

* The United States holds 240 prisoners at Guantanamo and has released or transferred to other governments about 530 other men and teenagers previously held there. Two were released by the Obama administration and the rest by the Bush administration.

* Charges were pending against 21 Guantanamo prisoners, though the Pentagon appointee overseeing the Guantanamo trials had referred only 14 cases to trial when the Obama administration froze the proceedings in January in order to rework the rules. The freeze has been extended until mid-September.

MOVES TO CLOSE GUANTANAMO

* Bush administration officials repeatedly said they wanted to close the controversial prison, but never advanced a plan to do so. They concluded in 2008 that closure would require legislation that was too difficult to negotiate in a heated election season.

* Shortly after taking office in January, Obama ordered the closing of Guantanamo. He set a one-year deadline for shutting the prison, barred harsh treatment of terrorism suspects held there and closed secret CIA jails overseas.