FACTBOX: Facts about the Guantanamo prison camp

(Reuters) - Five days of pretrial hearings began at the U.S. naval base at Guantanamo Bay in Cuba on Monday for Khalid Sheikh Mohammed, the self-styled architect of the September 11 attacks, and four other defendants accused of conspiring with al Qaeda to murder civilians.

No trial date has been set and the hearings are scheduled to be the last for the September 11 suspects before U.S. President-elect Barack Obama takes office on January 20.

Here are some facts about Guantanamo and Obama's position on its detention operation:

* The United States holds about 250 prisoners at Guantanamo and has released or transferred to other governments about 520 other men and teenagers previously held there.

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

* Obama has said he will close the Guantanamo detention operation and that U.S. civilian courts and the traditional military courts-martial system can handle detainee trials, rather than the separate system set up by President George W. Bush and Congress.

* The detention camp was set up 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 Pentagon plans to try as many as 80 prisoners but only two have been tried so far and a third pleaded guilty to supporting terrorism.

* Prosecutors are seeking the death penalty in six pending cases, including those of five men accused of plotting the September 11 attacks and one accused of masterminding the bombing that killed 17 U.S. sailors aboard the warship USS Cole in Yemen in 2000.

(Reporting by Jane Sutton in Miami and Donna Smith in Washington; Editing by John O'Callaghan)