US President George W Bush has defended his nominee for attorney general, Michael Mukasey, as he comes under pressure over his views on torture.
Mr Mukasey has lost the support of several Senate Democrats
Several Senate Democrats have said they will oppose Mr Mukasey's confirmation because of his refusal to say he believes water-boarding to be torture.
Mr Bush said it was unfair to ask him to comment on interrogation techniques on which he has not been briefed.
The US has not said whether it uses the technique, which simulates drowning.
The Senate Judiciary Committee is due to vote on Tuesday on whether to advance Mr Mukasey's nomination to the full Senate for confirmation.
The row over his position on water-boarding has thrown into doubt a process that seemed almost assured two weeks ago.
If confirmed, Mr Mukasey, a retired federal judge, will replace Alberto Gonzales, who resigned in August.
'Enemy out there'
Questioned by Democrats on the Senate committee, Mr Mukasey said in a written answer that he considered water-boarding, as it had been described, as "repugnant" and possibly "over the line".
However, he declined to explicitly rule the technique out as torture, saying he could not speculate on classified procedures.
Water-boarding simulates drowning by immobilising a prisoner with his head lower than his feet and pouring water over his face.
Mr Bush told reporters on Thursday that Mukasey was "not being treated fairly".
He said the judge had not been briefed on whether the US used water-boarding or not - adding that "the enemy" should not have that information either.
Speaking later to the Heritage Foundation, a conservative think tank, Mr Bush urged the Democratic-controlled Congress to confirm Mr Mukasey as a vital part of America's national security team.
Referring to the so-called "war on terror", Mr Bush insisted that the interrogation procedures used by the US were safe, legal and necessary - and provided very important information.
He also called on congressional leaders to renew legislation governing the gathering of intelligence and criticised their failure to pass bills to fund the wars in Iraq and Afghanistan.
Democratic Senator Sheldon Whitehouse said on Wednesday he would vote against Mr Mukasey's confirmation because his refusal to say water-boarding was "unconditionally wrong" would leave open the possibility of its use by US agencies.
Fellow Democrat Dick Durbin agreed: "As good as a person may be, his response to this question, this basic and fundamental question... leaves me with no alternative but to oppose Judge Mukasey's nomination."
At the time of Mr Mukasey's nomination in September, Mr Bush said he had the right qualifications for the job and was "clear-eyed about the threat our nation faces".
Mr Gonzales resigned after months of pressure over his role in the firing of federal prosecutors.