A courtroom artist's sketch, cleared by the U.S. Military, shows four of the Sept. 11 terrorist attack suspects at their arraignment before a military commission in Guantanamo Bay, Cuba, on Thursday. Khaled Sheikh Mohammed is at top left. (Brennan Linsley/Associated Press/Pool)

Khalid Sheikh Mohammed, the alleged mastermind of the attacks on the United States on Sept. 11, 2001, told a military tribunal at Guantanamo Bay naval base in Cuba that he's willing to face the death penalty if he's found guilty of the charges he faces.

Mohammed and four co-defendants are charged with conspiring to finance, train and direct the 19 hijackers who seized four airliners used in the attacks that destroyed the World Trade Center in New York and damaged the Pentagon outside Washington, D.C. They are charged in the deaths of 2,973 people killed in those two attacks and the crash of one airliner in Pennsylvania.

The U.S. government is seeking the death penalty for the accused men.

Asked by the judge, Col. Ralph Kohlmann, whether he understood that he faced capital punishment if convicted, Mohammed recited verses from the Qur'an and said he was willing to die.

"Yes, this is what I wish, to be a martyr for a long time," Mohammed declared.

He said he didn't want the U.S. military lawyers who've been appointed to represent him and would argue his own case, which the judge advised against. Prosecutors want the five accused to enter their pleas so their trials can begin later this year, but they are not required to respond to the charges.

The U.S. government says Mohammed, believed to be either 43 or 44, has confessed to approaching al-Qaeda leader Osama bin Laden in 1996 with an audacious plan to simultaneously hijack airliners and crash them into major landmarks in American cities.

A sketch by courtroom artist Janet Hamlin shows Khalid Sheikh Mohammed, right, and Waleed bin Attash, two of the co-conspirator suspects in the Sept. 11 attacks. They were attending their arraignment at the Guantanamo Bay U.S. Naval Base in Cuba on Thursday. (Brennan Linsley/Associated Press/Pool)

In transcripts of his confessions released in 2007, Mohammed was also said to have claimed responsibility for about 30 crimes, including the beheading of American journalist Daniel Pearl in Karachi, Pakistan, in 2002.

Mohammed was captured in Pakistan in March 2003 and taken to the Guantanamo Bay prison camp three years later. During that interlude, human rights groups say he was held in a unknown location and probably tortured to obtain his confessions.

U.S. authorities have admitted that the controversial simulated drowning technique known as "waterboarding" was used on Mohammed, but they say he wasn't subjected to severe physical pain or undue duress.

Mohammed lost his composure only after the judge ordered several defence lawyers to keep quiet.

"It's an inquisition. It's not a trial," Mohammed said in broken English, his voice rising. "After torturing they transfer us to inquisition-land in Guantanamo."

Mohammed, who appeared noticeably slimmer with a bushy grey beard and glasses, told the judge he believes only in Islamic Sharia law.

Confessions not admissible: lawyers

His military lawyers have said they will argue that Mohammed's confessions are not admissible as evidence because they were obtained illegally. They'll also challenge the military commission system itself, a trial process not used by the U.S. armed forces since just after the Second World War.

The administration of President George W. Bush has refused to put the Guantanamo detainees on trial in either the standard military justice system or a standard U.S. civilian court, arguing that they are unlawful enemy combatants and not entitled to the same rights as ordinary criminal defendants.

More than 60 U.S. and foreign journalists are covering Mohammed's appearance before the tribunal and his subsequent trial, which is expected to start in September.

The case will unfold in a highly secure courtroom with media kept in a separate area, or behind soundproof glass walls.

Concerns that Mohammed or his fellow defendants might divulge classified information about their interrogations or whereabouts will be addressed with a special microphone system that allows military censors to shut off audio feeds of their testimony. Closed circuit feeds to reporters in separate rooms are time-delayed by 20 seconds.

Other detainees in court

Military defence lawyer, Lt.-Cmdr. Charles Swift, says that's a violation of his client's rights.

"It may be an open trial when the government speaks," Swift said. "But when the defence speaks, when Khaled Sheikh Mohammed speaks, then they can decide it's classified information."

Four other detainees also accused of plotting the attacks were in court, including Ramzi Binalshibh, the alleged main intermediary between the 19 hijackers and al-Qaeda leaders.

Binalshibh, who had his ankles chained to the courtroom floor, said he deeply regrets not joining the hijackers who crashed passenger airliners into the World Trade Center, the Pentagon and a Pennsylvania field.

"I tried for 9/11 to get a visa but I could not," he said.

Asked if he understands that he could be executed if found guilty, Binalshibh said: "If this martyrdom happens today, I welcome it. God is great. God is great. God is great."

The other defendants are:

• Mustafa Ahmad al-Hawsawi, who allegedly trained hijackers.
• Ali Abd al-Aziz Ali, known as Ammar al-Baluchi, a nephew and lieutenant of Mohammed.
• Mustafa Ahmad al-Hawsawi, a Saudi, who allegedly helped finance the hijackers.

Death penalty questioned

There have also been criticisms of the U.S. government's intention to seek the death penalty against Mohammed and his co-defendants.

Maureen Basnicki of Toronto, whose husband Ken died in the collapse of the World Trade Center, says she has her doubts about the whole military commission process.

"I don't believe in capital punishment," she said, "and I don't know if justice can be done in such a trial."

Since the U.S. declared its intent to use the commissions to prosecute alleged al-Qaeda and Taliban operatives in 2003, there has been only one conviction. Australian David Hicks pleaded guilty to supporting terrorism in 2007 and was transferred to his home country to serve a short prison sentence. He is now free.

Canadian Omar Khadr is scheduled to go on trial for murder in such a commission later this year.

The U.S. military is pressing ahead with plans to prosecute about 80 of the roughly 270 men held at Guantanamo, despite repeated legal setbacks and a pending Supreme Court decision on detainee rights that could halt the proceedings.

U.S. Attorney General Michael Mukasey, defending military commissions to prosecute those charged with terror-related crimes, told federal judges Wednesday the upcoming trials will be "in the best traditions of the American legal system."

Speaking to a legal conference in Washington, Mukasey said the decision to try terror cases outside of civilian courthouses is not made lightly.

"Our nation and our constitution are never put in a more flattering light than when we prosecute in federal court those who have sworn to kill us," he said.

With files from the Associated Press