Graham, a South Carolina Republican, for the first time criticized the top generals removed by Bush from command in Iraq and said "a new team" must have the manpower to win the war.

"I support a surge with a purpose -- co-joining with the Iraqi political and military leadership to control this country," Graham said on NBC's "Meet the Press."

"We cannot let this country go into the abyss," he said. "Now is the last chance, and the only chance, to get this right."

In an address to the nation this week, Bush is expected to announce the dispatch of as many as 20,000 more troops to reinforce the 140,000 already in Iraq.

Graham, who has called for a troop increase for months, sparred with Sen. Joe Biden, a Delaware Democrat and the new Senate Foreign Relations Committee chairman.

Graham said there can be no political stability in Iraq unless the sectarian violence is stemmed.

Biden, confirming that he will run for president next year, said a renewed military push will be wasted without firm political measures. Iraqi Prime Minister Nouri al-Maliki, a Shiite Muslim, must stand up to Shiite militias and give Sunni Muslims heading the insurgency a real share of power, Biden said.

"We now have a civil war," Biden said. "All the king's horses and all the king's men will not put Iraq together again, absent Maliki making some very hard decisions about what he's going to do."

Graham, a member of the Senate Armed Services Committee, sharply criticized Democrats calling for a phased withdrawal from Iraq.

"These Democratic proposals are, to me, a formula for defeat," he said. "They are nothing more than just a political way to get out of Iraq, and it will come back to haunt us for years."

House Speaker Nancy Pelosi and Senate Majority Leader Harry Reid, the new congressional czars following the Democrats' election triumph in November, sent Bush a letter Friday saying, "After nearly four years of combat, tens of thousands of U.S. casualties, and over $300 billion dollars, it is time to bring the war to a close."

Biden declined Sunday to call for a troop withdrawal, using instead the formula "disengage and contain." Asked by "Meet the Press" host Tim Russert if he supports the Reid-Pelosi letter, Biden said, "I do not."

Graham vacillated, though, when asked whether the United States is losing the war.

"In all honesty, we are not winning, and if you're not winning, you're losing, and now is the time to come up with a strategy to win," Graham responded.

But later in the program, Graham said: "I don't think any Republican or Democrat should do anything right now to say the war is lost. We should try to win this war."

Graham, a first-term senator, has broken with Bush on key national security issues in the last two years, most prominently over how the United States should interrogate and prosecute accused terrorist detainees.

Now, his support for Bush's anticipated plan to send more troops to Iraq places him at odds with other prominent GOP senators. Sen. Richard Lugar, an Indiana Republican who was replaced by Biden as head of foreign relations panel, has declined to endorse a troop increase; GOP Sen. Chuck Hagel of Nebraska, also eyeing a White House run, called the idea "folly" and "Alice in Wonderland" last week.

While Bush unveils a new Iraq strategy this week, Biden said he and Lugar will begin hearings on the war. During the fall election campaign, Democrats accused the Republican-led Congress of having rubber-stamped Bush's war policies and abandoned meaningful oversight.

Graham took issue with conservative columnist Robert Novak's recent claim that only a dozen or so of the 49 GOP senators will support Bush's plan for a troop surge.

"I think there will be a lot of support by Republican members," Graham said.

Graham also defended Bush's move last week to overhaul Pentagon leadership of the war. Bush named Army Lt. Gen. David Petraeus to replace Gen. George Casey as the top military commander in Iraq, and he pegged Adm. William Fallon to follow Gen. John Abizaid as head of U.S. forces in the Middle East.

"We will hold the generals accountable for their work product," Graham said. "I respect General Casey and Abizaid, but the strategies they've come up with for the last two years (have) not worked."