WASHINGTON  - U.S. human rights groups reacted angrily to the Justice Department's announcement Monday that the self-acclaimed mastermind of the 9/11 attacks on Lower Manhattan and the Pentagon will be tried before a military commission at the Guantanamo detention facility in Cuba.

Obama U-turn: US to try 9/11 accused at Guantanamo The groups, which described the move as the latest in a series of reversals by the administration of President Barack Obama on the fate of Guantanamo detainees, charged that the decision was politically motivated and warned that it will prove counter-productive.

"The decision is clearly driven not by the nature of the alleged offence, or where and when it was committed," said a statement by the Center for Constitutional Rights (CCR), which has represented many of the detainees held at Guantanamo since the first terrorist suspects were brought there from Afghanistan and Pakistan in early 2002.

"[T]his flip flop on the part of the Obama administration is devastating for the rule of law and greatly undermines America's standing abroad," said Anthony Romero, the executive director of the American Civil Liberties Union (ACLU).

"Cases prosecuted by the Obama administration in the commissions now are sure to be subject to continuous legal challenges and delays, and their outcomes will not be seen as legitimate," he noted. "That is not justice. Americans deserve better."

In making the announcement that Khalid Sheikh Mohammed and four of his alleged co-conspirators will face trial by a military commission, Attorney-General Eric Holder expressed his own disapproval, blaming Congress for the decision which he said was made necessary due to legislation approved late last year that made it impossible for the defendants to be tried in a New York federal court as the administration had originally planned.

Led by Republicans and some New York Democrats, Congress passed a law banning the use of any appropriated funds to transport detainees held at Guantanamo to the United States or its territories.

Holder called Congress's action "unwise and unwarranted" but said the decision was made necessary because it was unlikely that the law could be amended or overturned "in the near future". He also reiterated the administration's determination to close Guantanamo which, in his inaugural speech in January 2009, Obama promised to achieve by the end of his first year in office.

"Members of Congress …have taken one of the nation's most tested counter-terrorism tools off the table and tied our hands in a way that could have serious ramifications," Holder said. "In reality, I know this case in a way that members of Congress do not."

He said the case against Mohammed was "one of the most well- researched and documented cases I have ever seen in my decades of experience as a prosecutor."

Like the human rights groups, he also pointed out that federal courts have successfully prosecuted hundreds of accused terrorists since the 9/11 attacks, the most recent in January, when a federal judge sentenced Ahmed Khalfan Gailani to life in prison without parole for his role in the 1998 bombings of the U.S. embassies in Kenya and Tanzania that killed some 224 people.

At the same time, military commissions, whose operations were suspended by Obama after taking office, have obtained only six convictions - four by plea bargain - that actually resulted in much lighter sentences due to doubts about whether the commissions' procedures could withstand scrutiny once they were appealed to federal courts.

While Holder expressed confidence in the ability of the commissions to provide a fair trial – their procedures and some protections for the defendants have been strengthened by Congressionally-enacted amendments to the Military Commissions Act in 2009 and by an executive order issued by Obama last month – the rights groups disagreed.

"Any trial in the military commission system will carry the stigma of Guantanamo, be subject to challenge and delay, and keep the world focused on how the defendants were treated rather than on the crimes they are accused of committing," said Andrea Prasow, senior counter-terrorism counsel at Human Rights Watch. "A verdict in the federal court system, in contrast, would be recognised throughout the world as legitimate."

Moreover, she said, "trying the 9/11 case in New York made sense because it is where the crime happened and where most of the family members of the victims live. Now, with the trial taking place on a military base, far away, many of those affected will be shut out of the process."

The groups also described Holder's own reaction as somewhat disingenuous.

"This administration had two years to bring [Mohammed] and his co-defendants to federal courts for trial, and failed to exercise its authority to do so," said Daphne Eviatar of Human Rights First. "It can still prepare to do so now and begin those trials as soon as the temporary ban Congress has imposed is lifted." The current legislation will expire at the end of September.

"This purely political decision risks making a second-class justice system a permanent feature of U.S. national security policy – a mistake that flies in the face of core American values and will undermine U.S. standing in the world," she said.

Republicans and other lawmakers who opposed a New York trial, on the other hand, praised the announcement. New York Senator Charles Schumer said Obama's original plan was "wrong-headed" and that a military trial would make it possible for Mohammed and his co-defendants to get the "ultimate penalty", an apparent reference to execution.

Some New York politicians had warned that the security- related costs of holding the trial in the city would run in the hundreds of millions of dollars.

In a joint statement, Republican Senator John McCain and Independent Democrat Joe Lieberman said it was "well past time to end debate over where the 9/11 conspirators should be tried and move forward with military commissions at Guantanamo."

But others said trying Mohammed in a military commission would give him a stature that he did not deserve. "Khalid Sheikh Mohammed is no warrior. He is a criminal and should not be treated otherwise through commissions," said ret. Gen. Joseph Hoar, a former chief of U.S. Central Command.

In addition to failing to close to Guantanamo and reactivating military commissions, Obama has disappointed rights activists by issuing orders that could justify indefinite detention of terrorist suspects subject to periodic administrative reviews.