The Kentucky Republican leader conceded that GOP lawmakers as well as Democrats are troubled by Bush's new policy, but said, "Congress is completely incapable of dictating the tactics of the war."

Reid has said he will schedule a vote on a nonbinding resolution expressing disapproval of Bush's new policy, but McConnell's filibuster threat indicated that he would not be rushed into the vote.

Meanwhile, Gates said he could not say just how long the buildup would last. "It's viewed as a temporary surge, but I think no one has a really clear idea of how long that might be," he told an early-morning White House briefing.

But he also said the United States should know pretty soon whether Iraqis were living up to their part of the deal and increasing their own forces.

Rice engaged in a tense exchange with Hagel, a Vietnam veteran and longtime critic of Bush's Iraq policy, disputing his characterization of Bush's buildup as an "escalation."

"Putting in 22,000 more troops is not an escalation?" Hagel asked. "I think, senator, escalation is not just a matter of how many numbers you put in."

"Would you call it a decrease?" Hagel asked.

"I would call it, senator, an augmentation that allows the Iraqis to deal with this very serious problem that they have in Baghdad," she said.

Hagel told Rice, "Madame Secretary, Iraqis are killing Iraqis. We are in a civil war. This is sectarian violence out of control."

She disputed that Iraq was in the throes of a civil war. To that, Hagel said, "To sit there and say that, that's just not true."

Sen. Bill Nelson, D-Fla., noted his own past support for the administration on the war. "I cannot continue to support the administration's position," he said. "I have not been told the truth over and over again by administration witnesses, and the American people have not been told the truth."

Meanwhile, after a meeting at the White House, Sen. John McCain, R-Ariz., expressed both doubts and optimism about the strategy.

"I am concerned about Maliki and his strength. I am concern as to whether these are sufficient number of troops," he said. "But I do think we can succeed."

McCain, a 2008 presidential contender, has been among a handful of lawmakers who have called for more - not fewer - US troops in Iraq.

In her testimony, Rice stressed Iraqi obligations for troops, money and the political will to allow the Bush plan to succeed. She promised oversight, without giving specifics.

"Iraqis are in the lead; we are supporting them," Rice said.

In speech in the House of Representatives, meanwhile, Rep. Ric Keller, R-Fla. noted that he was breaking ranks with Bush after long supporting the president's war policy.

"At this late stage, interjecting more young American troops into the crossfire of an Iraqi civil war is simply not the right approach," solution," Keller said.

A new AP-Ipsos poll found approval for Bush's handling of Iraq hovering near a record low - 29 percent of Americans approve and 68 percent disapprove.

In Wednesday's 20-minute speech, Bush took responsibility for mistakes in Iraq and outlined a strategy he said would pull it out of its spiral of violence.

"If we increase our support at this crucial moment, and help the Iraqis break the current cycle of violence, we can hasten the day our troops begin coming home," he said.

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