He said the fight against Islamic extremism must be joined with renewed fervor.

"The consequences of failure are chaos and disaster. And these people ... want to destroy the United States of America," McCain said.

His remarks came as Bush prepares to announce a shakeup of US Iraq policy, which reportedly could include sending tens of thousands of additional troops to supplement 140,000-strong US force already there.

But a troop surge has found little support in Congress, with McCain one of only very few voices speaking up in favor of such a policy.

McCain takes over this week as the top Republican in the Democrat-led Senate Armed Services Committee. The Democrats took control of the Senate and House of Representatives Thursday following their November elections triumph.

McCain said he believes US soldiers there are equally committed to the goal of fighting on in Iraq.

"I just recently visited them, including some who have been involuntarily extended," said McCain. "The morale is good. They understand what the mission is and they know what they need to do."

"I am convinced that if we leave and lose this conflict, the conflict will spread in the region, there will be chaos, and we will be sending in men and women into harm's way both in the region and other parts of the world," the former Navy pilot and former Vietnam prisoner of war told MSNBC.

"I've said for more than three years, it's long, hard, tough," McCain said.

"It's going to be very, very difficult. And we have to understand that. But we also have understand the sequences of failure."

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