Leading Senate Democrats, arguing that the chamber's GOP leadership has not pursued investigations on those matters, said they would push to establish a panel similar to the independent commission that investigated the al Qaeda attacks of September 11, 2001.

"We need the support of people around the world in our war on terrorism," said Sen. Carl Levin of Michigan, the ranking Democrat on the Armed Services Committee.

"The activities both at Guantanamo and at Abu Ghraib have cost us a great deal in that support," Levin said. "We've got to be willing to take a good hard look at ourselves and not leave all these gaps."

Allegations that Americans have tortured prisoners have dogged the Bush administration since April 2004, when graphic photographs of Army reservists mistreating prisoners at Iraq's Abu Ghraib prison outside Baghdad became public.

Many of the roughly 500 prisoners inside the U.S. military prison at the Guantanamo Bay, Cuba, naval station have been held for more than three years without being charged or having access to a lawyer. Most were captured in Afghanistan.

The U.S. Supreme Court on Monday agreed to hear the appeal of a former driver for Osama bin Laden, a Guantanamo detainee who is challenging the Bush administration's military tribunals for foreign terror suspects.

Levin said Democrats would try to attach a measure establishing an independent commission to a Pentagon spending bill now working its way through Congress.

Sen. John Warner, the Armed Services Committee's chairman, said Congress already has held dozens of open and closed hearings into allegations of abuse by U.S. troops and the CIA, and numerous investigations have found no policy condoning the mistreatment of prisoners.

Ninety-five troops have faced criminal charges for abusing detainees, and another 177 have received administrative punishment, said the Virginia Republican.

"An independent commission would send potentially the wrong message to our armed forces of our lack of confidence in their conduct and would seriously undermine ongoing intelligence-gathering activities," Warner said.

Information gathered in those interrogations "saves American lives," he said.

Speaking in Panama on Monday, President Bush told reporters, "We do not torture."

Bush, on his way home from a hemisphere conference in Argentina, was asked about reports of secret U.S. prisons in Eastern Europe and whether he would allow the Red Cross to access those sites.

He did not answer the question directly but said, "Any activity we conduct is within the law."

But Sen. Jay Rockefeller of West Virginia, the ranking Democrat on the Senate Intelligence Committee, said recent news reports about the use of "rendition" to transfer suspected terrorists to other countries and the reported detention of prisoners in former Soviet bloc countries have raised questions that Congress needs to get answered.

"If the Senate oversight committees are either unwilling or unable to tackle the tough but necessary questions associated with detention, interrogation or rendition of prisoners, then we should step aside -- regrettably, if we have to -- and let the work be done by others unfettered by other considerations," Rockefeller said.

Last month, the Senate overwhelmingly passed an amendment banning torture, despite White House opposition.

Vice President Dick Cheney has pushed for an exemption for prisoners interrogated by the CIA when there's believed to be risk of a terrorist attack.

But the measure -- sponsored by GOP Sen. John McCain of Arizona, a prisoner of war in Vietnam -- passed 90-9, with most Republicans supporting it.

Monday's volleys were the latest in a recent Democratic assault on the administration's management of the war in Iraq and against the al Qaeda terror network.

Last week, Democrats invoked a rarely used rule to close Senate doors and pressure Republicans to jump-start a stalled "Phase 2" probe into the Bush administration's use of the intelligence behind the 2003 invasion of Iraq.

Minority Leader Harry Reid said Congress should be willing to subpoena administration officials and documents in order to answer questions about how the White House built its case that war was necessary.

"We know the questions that must be asked," said Reid, a Nevada Democrat. "Now we need answers."

Intelligence Committee Chairman Pat Roberts, a Kansas Republican, said Sunday that last year's investigation of the faulty intelligence that indicated Iraq had been harboring weapons of mass destruction found no evidence of political pressure.

Democrats said the follow-up probe would focus on how the intelligence was used to sell the war rather than how it was developed.

Levin, who also sits on the Intelligence Committee, said Sunday that recently declassified documents from the Defense Intelligence Agency provide evidence that "the administration's prewar statements were deceptive."

Those documents indicate the administration continued to tout a report that Iraq had trained al Qaeda operatives to make chemical and biological weapons long after interrogators concluded the source of that report was probably lying to interrogators.

"If a policy-maker is making a statement based on erroneous intelligence, that's the fault of the intelligence," he told CNN Monday. "But that's not the situation here. Here the underlying intelligence said, 'Don't believe this guy.'"

Republicans hit back Monday by accusing Democrats of trying to score political points off continuing American losses in Iraq and of undermining support for U.S. troops.

Public support for the war in Iraq has sagged in the past year amid a persistent insurgency, despite the establishment of a transitional government and the adoption of a constitution.

Sen. John Cornyn, a Texas Republican, said Americans could face the human toll of the September 11 attacks "over and over and over again" if the United States withdraws prematurely from Iraq.

"I hope the members of this body who have politicized this issue by making false allegations of manipulation of intelligence would realize their allegations only serve to divide the American people and undermine critical American resolve to finish the important work we are about in Iraq," he said.