Mr Hamdan was brought before the five-member commission, the first since 1948, after eight months in solitary confinement and claims he has been beaten in custody.

The 34-year-old Yemeni was allegedly Osama bin Laden’s driver and bodyguard for five years from 1996. He has been charged with conspiring with al-Qaeda, which he knew had been involved in the attacks on US embassies in East Africa in 1998, on the warship USS Cole in 2000 and the September 11 attacks.

Prosecutors claimed that he had delivered weapons for al-Qaeda and bought and drove lorries that ferried bin Laden around, as part of his security tasks.

Mr Hamdan was allowed to shed his orange prison jumpsuit for the preliminary hearing and wear traditional Yemeni garb. He spoke little, just answering “la” and “na’am” for yes and no to initial questions about the hearing through an Arabic translator.

An armed guard sat near by, but Mr Hamdan appeared to be relaxed and gave a small wave after entering the room, set up in an old Second World War naval headquarters overlooking Guantanamo Bay.

About 60 people, including seven reporters, were allowed in. American troops armed with shotguns and machineguns patrolled the grounds outside the court.

His lawyer, Lieutenant-Commander Charles Swift, who has begun legal action in US federal courts challenging the commission as unconstitutional and illegal, quickly called for the disqualification of the presiding officer of the commission, Colonel Peter Brownback. He gave four reasons, including the fact that Colonel Brownback was the only lawyer, which, he said, would give him improper influence over the other commission members.

Despite his smiles, Mr Hamdan has lost 50lb in the past six months of solitary confinement, according to human rights lawyers. He has said in court documents made public this month that he was beaten and threatened with death by his interrogators.

In 2001, as US forces were fighting in Afghanistan, Mr Hamdan says that Afghan fighters captured him, tied him up and sold him to US forces. He also says that US officers in Afghanistan beat him, forced him to sit motionless for days and threatened him with torture, jail and death.

In a statement to a district court in Seattle, Mr Hamdan complained of the psychological pressure on him. “I have not been permitted to see the Sun or hear other people outside or talk with other people,” he said six months ago. “I am alone here except for a guard. One month is like a year here and I have considered pleading guilty in order to get out of here, after two months in solitary.”

Established by President Bush in 2001, the commissions have been lambasted as unfair because the military acts as prosecutor, judge and jury — and because the final appeal is to Mr Bush, who has called the Guantanamo inmates “killers”.

Yemeni security officials, speaking on condition of anonymity, said that Mr Hamdan had joined a Yemeni branch of the Egyptian militant group Islamic Jihad before al-Qaeda was formed in 1998.

Representatives from Amnesty International, the American Civil Liberties Union, Human Rights Watch, Human Rights First and the American Bar Association were being allowed to watch the hearings, but they were not allowed to see the prison or speak to panel members or prosecutors.

The International Committee of the Red Cross said that it was weighing whether to send an observer. The Geneva-based group has been the only independent organisation with access to the 585 prisoners accused of links to the Taleban or al-Qaeda.

Human rights groups have criticised holding the men as enemy combatants, a classification giving them fewer legal protections than prisoners of war. They also have questioned whether the commissions will be fair.

Two others charged with conspiracy are Ali Hamza Ahmad Sulayman al-Bahlul, 33, also of Yemen, and Ibrahim Ahmed Mahmoud al-Qosi, born in 1960. A fourth, David Hicks, 29, of Australia, faces charges of conspiracy to commit war crimes as well as aiding the enemy, and of attempted murder for allegedly firing at US or coalition forces in Afghanistan.

It could be months before the actual commissions begin.

Rules of evidence used in US courts and courts-martial will not apply and some groups express concern about the use of evidence obtained in interrogations. Some freed prisoners said they gave false confessions after interrogations lasting up to 14 hours.

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