"The president's view is that intelligence gathering is best left to the intelligence community," Burton said.

CIA report

Also on Monday, the US attorney-general Eric Holder selected John Durham, a federal prosecutor, to investigate cases of alleged abuses by the CIA and its contractors.

That followed a recommendation by the US justice department to consider re-opening several cases of prisoner abuse alleged to have been carried out by CIA employees in Iraq and Afghanistan. The cases were compiled five years ago, but have never been made public.

The justice department's decision came as it prepared to release further details of a 2004 CIA report on the use of and effectiveness of "enhanced interrogation techniques".

"The president has said repeatedly, he thinks that we should be looking forward, not backward... But ultimately the decisions on who's investigated and who is prosecuted are up to the attorney general"

Bill Burton, deputy White House spokesman

That document, which was authored by the then-CIA inspector-general, was released in May 2008, but only in a heavily edited form.

Fresh details from the report released by Holder could expose CIA employees and contractors to prosecution for their treatment of suspects.

Obama has said that those who interrogated terrorism suspects on legal guidelines written by the Bush administration should not face legal action, but Burton acknowledged that Holder has the final say.

"The president has said repeatedly, he thinks that we should be looking forward, not backward," Burton said.

"But ultimately the decisions on who's investigated and who is prosecuted are up to the attorney-general."

Holder reportedly says in his report that CIA staff threatened Abd al-Rahim al-Nashiri, an alleged al-Qaeda commander, with a handgun and an electric drill during a spell of interrogation.

Media reports say that Nashiri, who was captured in November 2002 and held at a CIA secret jail for four years, was one of three suspected al-Qaeda leaders who were waterboarded.

Waterboarding, a practice where a person's face is covered and water poured on to it to induce the fear of drowning, has been called a form of torture by human rights groups.