Hicks' lawyers and human rights monitors observing the hearings say the trials are rigged to ensure convictions and allow evidence to be submitted that has been obtained through coercion.
That he intentionally provided support to a terror organisation involved in hostilities against the United States.
That he provided support for preparation, or in carrying out, an act of terrorism.
Plea: Not guilty
The new tribunal was established by the US congress after the supreme court found the Pentagon's earlier version to be unconstitutional.
Speaking to reporters before Monday's arraignment hearing, Air Force colonel Morris Davis, the chief prosecutor for the tribunals, said prosecution planned to prove Hicks had provided "support for the al-Qaeda organisation".
Hick's lawyer told the judge his client pleaded guilty to a charge that says he intentionally provided support to a terror organisation involved in hostilities against the United States.
He denied a second charge that he provided supported for preparation, or in carrying out, an act of terrorism.
'Lack of safeguards'
Hicks was originally charged with war crimes and conspiracy to commit murder, and critics say the new charges are less specific.
|Hicks's father, Terry, was allowed to meet |
his son before the hearing [EPA]
Human rights groups have criticised the tribunal saying the process lacks legal safeguards, while the crime with which Hicks is charged did not even exist when he was captured in 2001.
Last year the US congress, then under a Republican majority, passed a law authorising a reconstituted tribunal regime with some adjustments but still operating outside of regular US courts or military courts-martial.
The law permits hearsay, evidence obtained through "coercion", to be admitted and forbids detainees from appealing against their detentions in US courts.
News of Hicks's guilty plea was welcomed by Australia's foreign minister who said he expected him to return home soon to serve his sentence in an Australian jail, under an agreement reached with Washington.
"My guess is he will be able to come back (to Australia) fairly soon," Alexander Downer told Australian Broadcasting Corp. radio.
Earlier Hicks's Australian lawyer, David McLeod, said Hicks was convinced he would not get a fair trial and might plead guilty if it would get him home sooner.
McLeod said there had been discussions about a potential plea agreement under which Hicks would receive a reduced sentence if he pleaded guilty.
During Monday's initial arraignment hearing Hicks told the judge he was satisfied with his Pentagon-appointed attorney but wanted more defence lawyers and paralegals "to get equality with the prosecution".
"I recognise that around the world, 'Guantanamo,' when you say the word, has a negative connotation"
Air Force Colonel Morris Davis,
the chief prosecutor
But the judge, marine colonel Ralph Kohlmann, said two civilian lawyers, including a defence department lawyer, were not authorised to represent him.
The two were ordered to leave the defence table when Hicks said he would not settle for them being designated as legal consultants.
One of the lawyers, Joshua Dratel, said he refused to sign an agreement to abide by tribunal rules because he was concerned the provisions do not allow him to meet with his client in private.
The US military flew Hicks' father and sister to the base and allowed them to meet privately with him in the court building before the hearing started.
Hicks has previously appeared before an earlier military tribunal system created by a presidential order, which the US supreme court later ruled unconstitutional.
Hicks is not accused of involvement in the September 11 attacks on New York and Washington DC and Human Rights Watch has said he could easily be tried in a regular US court.
Davis admitted critics had effectively turned public opinion against the Guantanamo tribunals but said he expected that to change once the military begins presenting evidence.
"I recognise that around the world, 'Guantanamo,' when you say the word, has a negative connotation," he said. "One thing I hope is that in the way we conduct these proceedings, maybe we can change some of those attitudes."