Hundreds of suspects are being held at Guantanamo Bay

It marks the first time Mr Bush has decided any terror suspects can be tried in a military court.

A decision on whether they will actually be tried will be made at a later date and will depend on moves by the suspects and their lawyers, the Associated Press news agency quoted an unnamed official as saying.

It is not clear who all the six suspects are or where they are being held, although the BBC has learnt that two of the men are the Britons Moazzam Begg and Feroz Abbasi. Another is believed to be Australian David Hicks.

Terror suspects detained in the US war on terror and held at Guantanamo Bay have been designated "unlawful combatants" without the right to a trial, causing concern among human rights organisations.

Two Britons are among those possibly facing a military tribunal

Mr Bush had already ordered the military to prepare for trials of suspects who are not United States citizens - and made it clear the death penalty could be applied.

Australian David Hicks, held prisoner since he was captured in Afghanistan while allegedly fighting for the Taleban, nearly two years ago is reported to be on the list.

The BBC's Red Harrison in Sydney says the Australian Government had not intended to reveal that Mr Hicks was on the list but his family and his lawyer had made it public.

'Real concerns'

The Australian Attorney General, Daryl Williams, said no charges have been laid against the six men, and the Americans have not revealed their names or said when the trials might be held.

But Mr Hicks's lawyer, Stephen Kenny, told the BBC that appearing before a military commission would be no more than a show trial.

The normal rules of evidence would not apply and the evidence would be presented to President Bush for his final determination, he said.

You have to worry very much that "evidence" is going to be brought before the military tribunal that has been extracted out of individuals Neil Durkin Amnesty International

The Attorney General says any suggestion of a conviction leading to a death sentence would not be supported by the Australian Government.

Neil Durkin, a spokesman for the worldwide human rights movement, Amnesty International, said they had real concerns over the use of military tribunals.

"If you have been held for over a year in legal limbo and you have been interrogated then you have to worry very much that "evidence" is going to be brought before the military tribunal that has been extracted out of individuals," he told BBC News Online.

"We want no use of material taken from people under those circumstances - we think it should be thrown out."

Cases examined

About 680 fighters allied with the former Taleban regime in Afghanistan and members of Osama Bin Laden's al-Qaeda network are being held in Guantanamo Bay.

Last month, trials for terror suspects who are not US citizens moved a step closer when the Pentagon named a chief prosecutor and defence counsel for cases dealt with by military commissions.

The new chief prosecutor, Colonel Fred Borch, said he was looking at more than 10 cases.

Some civil liberties activists fear al-Qaeda and Taleban suspects will not get a fair hearing, and have attacked provisions such as the right to closed hearings when secret evidence is given.

Colonel Will Gunn, the defence counsel, said he would push for trials to be as open as possible, saying the US would be judged on the fairness of the process.

Officials at Guantanamo Bay have reportedly begun planning for an execution chamber, should the death sentence be imposed.