'Incommunicado detention'

Tony Snow, a presidential spokesman, said the order barred "cruel, inhuman, or degrading treatment or punishment" and "acts of violence serious enough to be considered comparable to murder, torture, mutilation, and cruel and inhuman treatment".

"It also prohibits 'willful and outrageous acts of personal abuse done for the purpose of humiliating or degrading the individual in a manner so serious that any reasonable person, considering the circumstances, would deem the acts beyond the bounds of human decency'."

"And the order forbids acts intended to denigrate detainees' religion, religious practices, or religious objects," Snow said.

Jennifer Daskal, a senior counter-terrorism counsel with Human Rights Watch, said: "The key aspect of this is all the parts that aren't said."

Daskal said that the order allowed "a system of incommunicado detention to continue, with the blessing of the president.

"What we have here is an administration basically reciting a number of legal principles and saying "trust us." And that's hard to take from an administration that refuses to renounce waterboarding," she said.

Waterboarding is a practice in which a prisoner is tied down and water is poured over the face or over a cloth stretched over the face, producing the sensation of drowning.

Irreplaceable information

"Simply put, the information developed by our program has been irreplaceable"

Michael Hayden, CIA director

Michael Hayden, the director of the CIA, told employees in a statement that the order was necessary in order to make sure the detention and interrogation problem followed recent US Supreme Court rulings.

Hayden repeated the frequent cklaim made by the White House that Common Article III "contains vague language that has been subject to a variety of interpretations, not only within the US but internationally."

The order "gives us the legal clarity we have sought," Hayden said. "It gives our officers the assurance that they may conduct their essential work in keeping with the laws of the United States."

Hayden defended the usefulness of the program after the September 11, 2001 terrorist attacks, declaring: "Simply put, the information developed by our program has been irreplaceable.

"We have shouldered that responsibility for just one reason: to learn all we can about our nation's most deadly and fanatical enemies so that our operations to undermine them are as effective as possible."

Colonoscopy

Meanwhile Snow announced Bush is due to have a routine colonoscopy on Saturday and will temporarily hand presidential powers to Dick Cheney, the vice president, the White House said.

Snow said Bush will have the procedure at his Camp David mountaintop retreat.

He last had a colorectal cancer check on June 29, 2002. For the general population, a colonoscopy to screen for colon cancer is recommended every 10 years.

But for people at higher risk or if a colonoscopy detects precancerous polyps, follow-up colonoscopies often are scheduled in three to five year intervals.