Factbox: Guantanamo to host trial of Sept. 11 mastermind

(Reuters) - A war crimes tribunal will convene at the U.S. naval base at Guantanamo Bay in Cuba for the trial of Khalid Sheikh Mohammed, the self-described mastermind of the September 11, 2001, attacks on the United States, a U.S. official said Monday.

Here are some facts about the Guantanamo detention center and the war crimes tribunals.

* The detention camp opened in January 2002 after U.S.-led forces invaded Afghanistan. Many detainees were captured outside Afghanistan as part of what the United States called the "global war on terror" launched in response to the hijacked plane attacks that killed nearly 3,000 people in New York City, at the Pentagon outside Washington and in Pennsylvania on September 11, 2001.

* The U.S. military holds 172 captives at the detention camp, down from 245 when President Barack Obama took office in January 2009, according to the U.S. military. Nearly 800 prisoners have been held there.

* Three Guantanamo prisoners have pleaded guilty since Obama became president in January 2009. Obama tried unsuccessfully to shut down the Guantanamo detention camp. He also criticized the Guantanamo tribunals as a candidate and made some changes as president. Three other prisoners were convicted during the administration of President George W. Bush, who set up the camp in 2002 to hold, interrogate and try foreign captives suspected of links to al Qaeda and their Taliban protectors in Afghanistan.

* Obama missed his January 2010 deadline for shutting down the prison camp in part because Congress blocked funding for a plan to move detainees to a prison in the United States. His administration is still negotiating diplomatic deals to repatriate or resettle those cleared for release. About 30 prisoners were to be sent home to Yemen, but Obama suspended repatriations to that country after allegations that an al Qaeda affiliate in Yemen was behind a failed attempt to blow up a U.S. airplane on Christmas Day 2009.

* The Obama administration said on March 7 it had lifted its stay on military trials and the filing of new charges in the war crimes tribunals at Guantanamo Bay. Defense attorneys and leading human rights groups have long criticized the tribunals as a lesser form of justice that is rigged to convict defendants.

* Charges are expected to be filed soon against three prisoners already identified as eligible for trial. All three had previously been charged during the Bush administration but their cases were dropped in 2009 so the Obama administration could conduct a review of the Guantanamo detention policy. Following is a look at those three men.

* Abd al-Rahim al Nashiri -- a Saudi Arabian national of Yemeni descent, accused mastermind of the attack on the American warship USS Cole in 2000. The attack by a small, explosives-laden boat in the Yemeni port of Aden killed 17 U.S. sailors and wounded 47. Nashiri is accused of being al Qaeda's operations chief for the Arabian Peninsula. The CIA has acknowledged subjecting him to waterboarding, the simulated-drowning technique that human rights activists and others consider a form of torture. Polish prosecutors are investigating Nashiri's claims that he was tortured by interrogators at a secret CIA prison in Poland before he was moved to Guantanamo. He was captured in Dubai in 2002. The original charges under the Bush administration carried the death penalty.

* Ahmed al Darbi -- a Saudi Arabian accused of buying a boat and global positioning devices and recruiting crew members as part of an unrealized plot to ram an explosives-laden boat into an unidentified ship in the Strait of Hormuz. A lawyer familiar with the case said Darbi was given $50,000 to further the plot but spent it on prostitutes and drugs. Darbi has said he used his boat only to ferry sheep across the strait. Darbi is also accused of teaching at an al Qaeda camp in Afghanistan and meeting Osama bin Laden there. He was captured in Azerbaijan in 2002.

* Obaidullah -- an Afghan who uses only one name. He is accused of working with al Qaeda in Afghanistan, hiding mines and other explosives at his residence and having a notebook that included instructions on how to use them. Obaidullah has said the mines belonged to a commander who lived in the house during the Soviet occupation, and that he had the notes only because the Taliban forced him to attend a bomb detection class. He was captured in Afghanistan in 2002.

(Reporting by Jane Sutton; Editing by Tom Brown and Will Dunham)