The self-professed architect of the September 11 attacks Khalid Sheikh Mohammed and four co-defendants said they would confess to terror charges that could bring the death penalty but postponed their guilty pleas.

"The accused in this case had decided that they wished to withdraw all motions ... and wished to enter pleas in what was termed as confessions in this case," said Army Colonel Stephen Henley, the judge of the military tribunal at the US naval base at Guantanamo Bay, Cuba in pre-trial proceedings.

He also read out a letter submitted by the defendants that they wished to dismiss their tribunal-appointed attorneys, scrap pre-trial motions and plead guilty to the terror charges.

september 11 2001 terror attack suspect pleads guilty 091208 02 But after a recess, Sheikh Mohammed ( right ) and two co-defendants changed tack, saying they were postponing their guilty pleas pending mental competency evaluations of the two other defendants, Ramzi bin al-Shibh and Mustafa al-Hawsawi.

"I think I would like to withhold or postpone our pleas until after the decision is made about our other brothers bin al-Shibh and Hawsawi," Sheikh Mohammed told the judge.

Walid bin Attash and Ali Abdul-Aziz Ali also postponed, with Ali saying the move signaled the desire to present a united front in the tribunal. "Our plea request is based on joint strategy," Ali said.

The three indicated they still intended to plead guilty but will not do so until they find out whether the two other defendants will also be allowed to sack their lawyers, withdraw their motions and plead guilty.

"We don't want to waste time," Sheikh Mohammed earlier told the judge in English. He appeared before the court dressed in white and wearing a white turban, with a long gray and black beard.

"I don't appreciate between the judge and my attorney and (US President George W.) Bush and the CIA who tortured me," he said, adding that he also did not trust Henley.

Held in secret prisons and tortured

Sheikh Mohammed, captured in Pakistan in 2003 and handed over to US agents who held him in secret prisons for more than three years before sending him to the detention facility at Guantanamo Bay, is known to have been subjected to harsh treatment by the CIA, including "waterboarding," or simulated drowning, leading to controversy about the admissibility of his reported confession.

september 11 2001 terror attack suspect pleads guilty 091208 01 The judge had allowed Sheikh Mohammed, bin Attash and Ali to withdraw all their motions and go to pleas, but he refused to allow the same for two other defendants on concerns they were not mentally competent.

"The law compels me to order some additional testing" on the mental competency of Mustafa al-Hawsawi, Henley said after the defendant's US-appointed lawyer requested a medical evaluation.

It was not clear exactly when the formal guilty pleas would be entered for the first three defendants and, if allowed, the other two undergoing evaluation.

But with the judge postponing argument on the case's motions - and proceedings shifting to testimony of four witnesses involved in the influence of an Office of Military Commissions legal advisor over prosecution teams - there was growing expectation that pleas would not be entered this week, and increasing likelihood that they would not be heard until the next year.

The five men, all formally charged in June, were watched at the tribunal proceedings by five relatives of those killed on 9/11. The victims' kin sat in the back of the courtroom behind transparent acrylic glass.

Relatives of victims observe trial

It is the first time that relatives of those killed in the 2001 attacks in New York and Washington have been allowed to observe a trial in Guantanamo.

september 11 2001 terror attack suspect pleads guilty 091208 03 Alice Hoglan, mother of 9/11 victim Mark Bingham, said she was "really proud that the commission is proceeding in its slow and thoughtful and deliberate way, despite the histrionics of these guys."

"I've had quite a long time to think about this moment and I'm not surprised to see how hostile they are," she said.

Human rights groups groups quickly blasted the proceedings.

"What should have been a major victory in holding the 9/11 defendants accountable for terrible crimes has been tainted by torture and an unfair military commissions process," said Human Rights Watch official Jennifer Daskal.

"Anyone who believes that this is a victory for American justice is sadly mistaken," American Civil Liberties Union executive director Anthony Romero said.