Sen. John McCain argued Sunday that America's image abroad could be ruined if Congress doesn't ban the torture of prisoners in U.S. custody.

McCain, who was tortured during the Vietnam War, is the leading supporter of a provision banning such inhumane treatment.

White House officials, however, have threatened a presidential veto of any bill with restrictions on handling detainees, saying it would limit the president's ability to protect Americans and prevent a terrorist attack.

"If we are viewed as a country that engages in torture ... any possible information we might be able to gain is far counterbalanced by (the negative) effect of public opinion," McCain, R-Ariz., said on CBS' "Face the Nation."

Terrorists are "the quintessence of evil," he said. "But it's not about them; it's about us. This battle we're in is about the things we stand for and believe in and practice. And that is an observance of human rights, no matter how terrible our adversaries may be."

The Republican-led Senate has approved McCain's provision -- an instance of rare defiance of President Bush's wartime authority.

But prospects of the bill clearing the House of Representatives are uncertain. Vice President Dick Cheney has vigorously lobbied Congress to drop or modify the detainee provisions, and wants to exempt the Central Intelligence Agency from the proposed torture ban.

McCain said he hopes to reach a compromise with the White House. But he said that after the discovery of widespread prisoner abuse at the Abu Ghraib facility in Iraq, public opinion about the United States has plummeted worldwide.

"We've got two wars going on: one a military one in Iraq, and then we've got a war for public opinion, for the hearts and minds of all the people in the world," McCain said. "We've got to make sure that we don't torture people."

Stephen Hadley, Bush's national security adviser, said on a cable news channel that the White House was working with McCain and other lawmakers to "come up with an approach that both allows us to do what we need to do to defend the country against terrorist attack and, at the same time, make good on the president's commitment that we will not torture and we will act within the bounds of law."

Hadley went on to describe a hypothetical situation that imagined one of the Sept. 11, 2001, terrorists had been arrested a few days before the attacks.

"It's a difficult dilemma to know what to do in that circumstance to both discharge our responsibility to protect the American people from terrorist attack and follow the president's guidance of staying within the confines of law," he said. "These are difficult issues."

Democratic Sen. Carl Levin, however, said it's "unthinkable that the vice president of the United States continues to insist upon an exception for the CIA, saying they should not be bound by our torture policy."

"Torture can't be justified," he told a cable news show.