US President George W Bush has rejected claims his administration uses torture and defended the CIA's methods.
Mr Bush said members of Congress had been told about the techniques
He was responding to a New York Times report that the US Justice Department secretly authorised harsh interrogation techniques for terror suspects in 2005.
The alleged 2005 memo came months after a 2004 opinion in which the Justice Department declared torture abhorrent.
Mr Bush said: "This government does not torture people. We stick to US law and our international obligations."
According to the New York Times, the interrogation techniques endorsed by a 2005 Justice Department memo were some of the harshest ever used by the CIA.
They included head-slapping, exposure to freezing temperatures and simulated drowning, known as water-boarding.
'Protecting the people'
The 2005 legal opinion was reportedly issued shortly after former Attorney General Alberto Gonzales took over the Justice Department.
A second memo issued later that year advised that none of the techniques in use by the CIA would breach anti-torture legislation before Congress that barred "cruel, inhuman and degrading" treatment of prisoners, the New York Times said.
Its report also cited officials saying that the CIA had returned in summer 2007 to its practice of holding terror suspects in secret prisons overseas.
In a hastily arranged press appearance on Friday, Mr Bush defended his administration's methods and said interrogations were carried out by "highly-trained professionals".
"When we find somebody who may have information regarding an attack on America, and you bet we're going to detain them, you bet we're going to question them," he said.
"The American people expect us to find out information, this actionable intelligence, so we can help protect them. That's our job."
The techniques used had been "fully disclosed to appropriate members of the United States Congress", he added.
Democrats in both the Senate and the House of Representatives on Thursday demanded to see the two alleged secret memos from 2005.
Several Republicans have said they were satisfied with those briefings but a handful have joined with Democrats in expressing their concern, says the BBC's Jamie Coomarasamy in Washington.
The politicians suggest that the administration many not have been forthcoming enough, or may even have condoned techniques that overstepped the boundaries of legality, our correspondent says.
The issue of detainee interrogation is now likely to figure even more prominently in the confirmation hearings of Mr Bush's nominee for attorney general, Michael Mukasey, due to begin later this month, he adds.