U.S. President George Bush signed an executive order Friday prohibiting cruel and inhuman treatment, including humiliation or denigration of religious beliefs, in the detention and interrogation of suspects in extremist attacks.

The White House declined to say whether the CIA currently has a detention and interrogation program, but said if it does it must adhere to the guidelines outlined in the executive order. The order covers captured al-Qaeda members who have information on attack plans or the whereabouts of the group's senior leaders.

"Last September, the president explained how the CIA's program had disrupted attacks and saved lives, and that it must continue on a sound legal footing," White House press secretary Tony Snow said. "The president has insisted on clear legal standards so that CIA officers involved in this essential work are not placed in jeopardy for doing their job — and keeping America safe from attacks."

The United States has been criticized over interrogation techniques such as "waterboarding," in which prisoners are strapped to a plank over water and are made to fear that they may be drowned.

Critics also have complained that the CIA has run secret prisons on European soil and mistreated prisoners during clandestine flights in and out of Europe.

Bush has repeatedly said that the United States does not practise torture.

The White House did not detail what types of interrogation procedures would be allowed.

But it did offer parameters, saying any conditions of confinement and interrogation practices could not include:

• Torture or other acts of violence serious enough to be considered comparable to murder, torture, mutilation and cruel or inhuman treatment.
• Willful or outrageous acts of personal abuse done to humiliate or degrade someone in a way so serious that any reasonable person would deem the acts to be beyond the bounds of human decency, such as sexual or sexually indecent acts undertaken for the purpose of humiliation, forcing the individual to perform sexual acts or to pose sexually, threatening the individual with sexual mutilation.
• Acts intended to denigrate the religion, religious practices, or religious objects of an individual.

The order also says that detainees must receive basic necessities, including adequate food and water, shelter from the elements, necessary clothing, protection from extreme heat and cold and essential medical care. It says whatever interrogation practices are used must be determined safe on an individual basis.

To ensure the professional operation and safety of the program, it directs the CIA director to issue written policies to govern the program, including guidelines for CIA personnel.