The Pentagon on Monday charged the alleged planner of the September 11 attacks, Khalid Sheikh Mohammed, and five others with murder and conspiracy and asked that they be executed if convicted.

The charges are the first from the Guantanamo war court alleging direct involvement in the 2001 attacks on the United States and the first involving the death penalty.

Mohammed, a Pakistani national better known as KSM, has said he planned every aspect of the September 11 attacks.

But his confession could be problematic if used as evidence because the CIA has admitted it subjected him to "waterboarding" - an interrogation technique of simulated drowning that has been widely criticized as torture.

The rules of the court on the U.S. naval base at Guantanamo Bay, Cuba, prohibit the use of evidence gained through torture, as does an international treaty the United States has signed.

But Brig. Gen. Thomas Hartmann, a legal adviser at the Guantanamo prison camp, would not rule out the use of evidence gathered during the CIA interrogation of Mohammed.

"The question of what evidence will be admitted, whether (involving) waterboarding or otherwise, will be decided in the court," he said.

Relatives of those killed in the attacks were divided over the Pentagon's decision to seek the death penalty.

But civil rights groups questioned whether the suspects could get a fair hearing and said the death penalty should not be considered under a court system they called flawed.

The charges must be approved by a Pentagon appointee who oversees the court before a trial can be ordered.

2,973 MURDER COUNTS

Military prosecutors want to try all six defendants together - Mohammed, Ali Abdul Aziz Ali, Mohammed al-Qahtani, Ramzi Binalshibh, Mustafa Ahmed al-Hawsawi and Walid bin Attash.

The charges include conspiring with al Qaeda to attack and murder civilians and 2,973 counts of murder for those killed in the September 11 attacks, when four hijacked passenger planes slammed into New York's World Trade Centre, the Pentagon and a field in Pennsylvania.

Suspects were also charged with terrorism, violating the laws of war and targeting civilians.

"Obviously 9/11 was a defining moment in our history and a defining moment in the global war on terror, and this judicial process is the next step in that story of our history on this issue," said White House spokeswoman Dana Perino.

The White House had no role in deciding who would be prosecuted or to seek the death penalty, Perino said.

'NO SECRET TRIALS'

Washington has faced fierce criticism worldwide for the detention without charge - often for years - of suspected al Qaeda and Taliban members at Guantanamo. The trial system for Guantanamo prisoners has been denounced too.

The Guantanamo tribunals are the first U.S. war crimes tribunals since World War Two. They were established after September 11 to try non-American captives whom the Bush administration considers "enemy combatants" not entitled to the legal protections granted to soldiers and civilians.

Anthony Romero, executive director of the American Civil Liberties Union, said a credible trial was impossible because the system lacks basic due process protections.

Human Rights Watch said the cases should be moved to federal civilian court.

"If trials are held in Guantanamo by flawed military commissions, the system will be on trial as much as the men being accused of horrific crimes," said Jennifer Daskal, senior counterterrorism counsel at Human Rights Watch.

Still, the Pentagon said the trials, authorized by Congress, would follow the rule of law and be "as completely open as possible." Hartmann said defendants and their counsel would see even classified evidence used against them in court.

"There will be no secret trials. Every piece of evidence, every stitch of evidence, every whiff of evidence that goes to the finder of fact, to the jury, to the military tribunal, will be reviewed by the accused," Hartmann said.