Ibrahim al-Qosi, a Sudanese prisoner at the US military prison in Guantanamo Bay, Cuba, has pleaded guilty to providing material support to al-Qaeda.
Al-Qosi, who was detained for more than eight years before the conviction, admitted that he was cook and driver to Osama bin Laden, the leader of al-Qaeda.
The conviction is the first in a military tribunal since Barack Obama became the US president in January 2009.
Al-Qosi faces life in prison, or he could be released for time already served.
The US defence department said in a statement that the tribunal process safeguarded “the rights of the accused”.
Al Jazeera’s Nick Spicer reports.