"Under commission rules the military judge must be satisfied that Hicks' guilty plea is voluntary and otherwise lawful"
Bryan Whitman, Pentagon spokesman
The defense and prosecution were expected to discuss details of Hicks' guilty plea on Tuesday before presenting it to the military judge for a decision later this week, Bryan Whitman, a Pentagon spokesman, told reporters.
"Under commission rules the military judge must be satisfied that Hicks' guilty plea is voluntary and otherwise lawful," Whitman said.
Hicks father, Terry, meanwhile has told US media he believes his son struck a bargain with prosecutors to get out of Guantanamo.
"It's a way to get home, and he's told us he just wants to get home," said Terry.
Last October, George Bush, the US president, made law a new military tribunal after the supreme court ruled the previous commission unconstitutional.
The new system is also being challenged by lawyers for Guantanamo detainees who are asking the court to intervene and guarantee their clients' right to challenge their confinement in civilian courts.
Critics have said Monday's guilty plea reflects Hicks' despair at his prospects for obtaining a fair trial from the Guantanamo military tribunal.
"He and his attorneys knew he could not receive a fair trial, so Hicks pleaded guilty," said Marine Lieutenant Colonel Colby Vokey, the lawyer for Omar Khadr, a Canadian Guantanamo detainee who is expected to face charges before the commission.
Hicks, 31, has denied a second charge of supporting terrorism by allegedly attending training in Afghanistan and reporting to an al-Qaeda commander after the World Trade Centre attacks in September 2001.