President Bush's nominee for attorney general has denied paving the way for US prisoner abuses and dismissing the Geneva Conventions as "obsolete".
Alberto Gonzales says the US has never had a policy of torture
Alberto Gonzales, currently the president's chief legal adviser, has been accused of giving the green light for violent treatment of detainees.
At his Senate confirmation hearing, he insisted: "Torture and abuse will not be tolerated by this administration."
He faced tough questions as the two-day hearing got under way on Thursday.
A senior senator on the Senate Judiciary Committee, Democrat Patrick Leahy, said the Bush administration in its first four years had set out to "minimise, distort and even ignore our laws, our policies and international agreements on torture and treatment of prisoners".
"America's troops and citizens are at greater risk because
of those actions," he said.
Democratic Senator Edward Kennedy said: "The issue of your commitment to the rule of law is what most concerns us."
Mr Gonzales' opponents say his advice that the Geneva Convention on treatment on prisoners of war did not apply to terrorist suspects led to human rights abuses like those at Abu Ghraib prison in Iraq.
They have cited two memos. One said the Geneva Conventions were being "rendered obsolete" by the new type of war America was fighting, the other apparently narrowed the definition of torture.
The Texan judge defended a robust US policy on terror suspects, but denied that it was responsible for the Abu Ghraib scandal, which he said was "simply people who were morally bankrupt having fun, and I condemn that totally".
Mr Gonzales told the Senate: "I am deeply committed to ensuring that the US government complies with all its legal obligations... [including] of course the Geneva Conventions whenever they apply."
He said after the attacks of 11 September 2001, government lawyers had to make "fundamental decisions" on how to apply treaties and US law to an unconventional enemy, and that "the Department of Justice's top priority is to prevent terror attacks against our nation".
Even those who posed hostile questions in the Senate praised Mr Gonzales' character and his progress from an extremely poor immigrant family, via Harvard University, to become a Texas Supreme Court justice.
His opponents concede that they are not likely to prevent his appointment as the successor to Mr Bush's first attorney general, John Ashcroft.