The US Senate has voted to bar the CIA from using harsh interrogation techniques such as simulated drowning, widely known as water-boarding.
The ban was contained in a broader intelligence bill that passed 51-45.
The Senate vote follows a similar move by the House of Representatives in December, despite a threat by President George W Bush to veto such legislation.
A senior justice department official is set to testify later in the day that water-boarding is now not legal.
"The set of interrogation methods authorised for current use is narrower than before, and it does not today include water-boarding," says Steven Bradbury, the acting head of the Department of Justice's Office of Legal Counsel.
His remarks, obtained by the Associated Press, were prepared for an appearance before the House Judiciary Constitution subcommittee later on Thursday.
He goes on: "There has been no determination by the justice department that the use of water-boarding, under any circumstances, would be lawful under the current law."
Water-boarding, condemned as torture by rights groups and many governments, is an interrogation method that puts the detainee in fear of drowning.
In a vote that split largely along party lines, the Democratic-led Congress on Wednesday passed a bill that would restrict the CIA to using the 19 interrogation techniques outlined by the US Army field manual.
The legislation would ban the CIA from using not only water-boarding but sensory deprivation and other harsh coercive methods on prisoners.
"There must be no doubt in the world that this great nation does not torture," said Senator Chuck Hagel, one of the bill's main sponsors.
Senator John McCain, who is the front-runner for the Republican presidential nomination and who has previously brought anti-torture legislation, voted against the overall bill.
"I made it very clear that I think that water-boarding is torture and illegal, but I will not restrict the CIA to only the Army field manual," he said.
Last week, the CIA publicly admitted for the first time using water-boarding on terror suspects.
The CIA director, General Michael Hayden, told the House Intelligence Committee the technique had only been used on three people, including high-profile al-Qaeda detainee Khalid Sheikh Mohammed, and not for the past five years.
He said that water-boarding may no longer be legal given changes in US legislation and that the CIA would respect limits passed by Congress even if it meant failing to get crucial information.
Gen Hayden has argued that the CIA has different interrogation needs than the army and requires more latitude to be effective.
The Senate vote fell short of the two-thirds majority needed to override a presidential veto, which Mr Bush has threatened to use.
"Part of this bill are inconsistent with the effective conduct of intelligence gathering," White House spokesman Tony Fratto said.
CIA 'ENHANCED INTERROGATION' TECHNIQUES
- Water boarding: prisoner bound to a board with feet raised, and cellophane wrapped round his head. Water is poured onto his face and is said to produce a fear of drowning
- Cold cell: prisoner made to stand naked in a cold, though not freezing, cell and doused with water
- Standing: Prisoners stand for 40 hours and more, shackled to the floor
- Belly slap: a hard slap to the stomach with an open hand. This is designed to be painful but not to cause injury
Source: Described to ABC News by un-named CIA agents in 2005
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