The United States has regarded him as one of the most dangerous men in the world, a sworn enemy who plotted the September 11, 2001, terrorist attacks, which killed nearly 3,000 people...

Now, the United States is asking Khalid Sheikh Mohammed to safeguard some of its national security secrets. That's part of the rules Mohammed must follow after being granted the right to represent himself before a military tribunal that could hand him the death penalty.

It was also one of the more bizarre twists as Mohammed and four other co-defendants appeared Thursday for the beginning of their tribunal and for the first time in public after years of secret confinement.

The more than six-hour proceedings at the US Navy base at Guantanamo Bay in remote Cuba featured a host of strange events, from Mohammed insisting a sketch artist redo his nose before the image went public to another defendant wanting to know what would happen to his body if he was executed.

But little stood out more than toward the end of the process when, after a request from the judge, Ralph Kohlmann, Mohammed promised to protect classified information that is off-limits to the American public.

'It was weird conceptually,' said Joanne Mariner, a director at Human Rights Watch who observed the arraignment. 'It was one of incongruous moments of the hearing.'

Under the rules of the military tribunals, the Pentagon said the defendants would have access to all of the evidence presented in court, even if it is classified. The military said the rule would help guarantee the suspects get a fair trial although that assessment has been challenged by human rights groups.

Mohammed was one of three defendants granted permission to represent themselves who promised to not reveal secret information at the trials.

When classified information needs to be presented, both sides are required to inform Kohlmann, a Marine colonel, in advance so he would be able to suspend public viewing of the proceedings.

There is a button in the courtroom the judge can order pushed to shut off the closed-circuit telecast to the media centre about 200 yards away from the proceedings. It also cuts off the audio feed into the press box inside the courtroom.

The Pentagon said it had to balance the need to allow defendants to see classified evidence that could be used in the courtroom with the need to keep it out of the public eye, even if that means it falls into the hands of individuals like Mohammed and other terrorist suspects seen as some of the worst enemies in recent US history.

'They are entitled to it if we are going to use it in trial,' said Major Gail Crawford, a spokeswoman for the tribunals. 'That's our system of justice. You have to decide what's more important.'

But even if Mohammed and his cohorts do get to see the classified material, there's a good chance they won't be taking it off Cuba. If he is acquitted before the tribunal, the US military could continue holding him as an enemy combatant in the war on terrorism, a struggle many believe won't ever end.