The campaign for the ban has been led by Republican Senator John McCain, who secured a landmark agreement on the ban with President George W. Bush on Thursday, but doubts have been expressed whether it will really stop detainee abuse.

Representative Duncan Hunter, chairman of the House of Representatives Armed Services Committee, had threatened to block the bill unless it gave sufficient legal protection to US forces.

He had also sought guarantees that the law would not inhibit US intelligence gathering in the "war on terror".

Hunter said he withdrew the threat to block the measure after John Negroponte, the director of national intelligence, promised to provide a report on the impact of the new law within 180 days.

US news outlets have expressed some scepticism that the new law would have a major impact on the international US reputation, tarnished by the Abu Ghraib scandal, reports of secret CIA prisons in Europe and alleged abuses at the Guantanamo Bay "war on terror" prison camp.

"Mr Bush had barely announced his deal with Mr McCain before Attorney General Alberto Gonzales made it crystal clear that the administration would define torture any way it liked," said a New York Times editorial.

Gonzales told CNN television, "Congress has defined what torture is, and it is intentional infliction of severe -- I emphasize the word 'severe' -- intentional infliction of severe physical or mental pain or suffering."

When questioned about the use of "waterboarding", a practice in which interrogators make detainees think they are drowning, Gonzales would not say whether it would be considered torture.

"That would be something that would have to be evaluated on a case-by-case basis," added Gonzales, who refused to talk about individual techniques.

The Times said Hunter's objections to the law were "a smokescreen".

Human Rights Watch charged that the same legislation that includes the McCain amendment also includes another provision that would deny detainees held at the Guantanamo Bay prison the right to legal action if they are mistreated and effectively allows the Department of Defense to consider evidence secured through torture or other inhumane treatment.

"If passed into law, this would be the first time in American history that Congress has effectively permitted the use of evidence obtained through torture," the New York-based rights watchdog said in a statement.

The Washington Post called the proposed law "an important step toward curtailing the systematic human rights violations committed by the Bush administration in its handling of foreign prisoners."

But it called for an "aggressive" follow-up by Congress to make sure all CIA interrogation methods are reviewed.

"Restoring the rule of law over an administration that deliberately chose lawlessness in its treatment of detainees may be an arduous process," warned a Post editorial.

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