WASHINGTON - President Bush is telling lawmakers he will send thousands more US troops to Iraq's two most troubled regions, in a plan that Democrats are resisting as a major escalation of a 31/2-year-old war.

Bush on Wednesday will announce a new war strategy and is expected to call for as many as 20,000 additional troops, according to several senators briefed by the president on Monday.

The extra forces would be sent to Baghdad, which has been consumed by sectarian violence, and the western Anbar Province, a base of the mostly Sunni insurgency and foreign al-Qaida fighters, Sen. Kay Bailey Hutchison, R-Texas, and others said following the session with Bush.

A day before Bush's nationally televised speech describing his proposal, Sen. Edward Kennedy, a longtime critic of Bush and the war, will propose legislation denying him the billions needed to send more troops to war unless Congress agrees first. Though it was unclear whether the bill would ever reach the full Senate, it could at least serve as a rallying point for the most insistent foes of the Iraq conflict.

Democrats seem divided on whether to block funds for troop increases, but many were not ruling it out. Senate Majority Leader Harry Reid, D-Nev., said Democrats would "look at everything" in their power to curb the war, short of cutting money for troops already in the field.

Sen. Carl Levin, D-Mich., the new chairman of the Armed Services Committee, said he would only consider an increase in US forces in Iraq if Bush agreed to start withdrawing troops within six months.

"We've got to focus the attention of the Iraqis on their responsibility for their own country," Levin told the Detroit Free Press. "The only way to tell them is that we're going to redeploy our forces in 4 to 6 months."

The bill by Kennedy, D-Mass., is guaranteed to fuel the debate among lawmakers on how far they should go to try to force the president's hand on the unpopular war.

Under the Constitution, the president has broad war-making powers, while Congress controls spending. Democratic leaders have swiftly rejected any suggestion of withholding money from troops already in combat zones.

"The Congress has the power of the purse and what we are saying is before the president sends additional American troops into the civil war, the president has to come back to the Congress and get the authority for that deployment," Kennedy said Tuesday on NBC's "Today" show.

"The American people ought to have a voice and a vote and members of Congress should be held accountable. We ought to take this step and stop the surge," Kennedy said.

In prepared remarks he was to deliver later Tuesday to the National Press Club, Kennedy said: "The best immediate way to support our troops is by refusing to inject more and more of them into the cauldron of a civil war that can be resolved only by the people and government of Iraq."

If brought to the floor by Democratic leaders, Kennedy's proposal would force Republicans to put themselves on record regarding the war for the first time since the Nov. 7 elections, when the GOP lost control of Congress to the Democrats in large part because of the war. Most Republicans say they back the president, or are at least willing to hear him out, but a few GOP moderates say there is no indication US troops would make a difference.

According to senators who attended the meeting Monday with the president, a promise to send more troops to Iraq would be conditioned on criteria met by the Iraqi government, such as reaching political deals on sharing the nation's oil resources and dispatching more of its own troops to Baghdad.

Bush told the senators that Iraqi Prime Minister Nouri al-Maliki suggested the plan when the two met in late November in Amman, Jordan. The senators said the president expressed confidence that the Iraqi government could meet certain milestones in exchange for additional US support.

But several of the senators remained skeptical.

"We've had these benchmarks before and to no avail," Sen. Olympia Snowe, R-Maine, said after meeting with Bush. "Why should we increase our exposure to risk?"

But whether Snowe and other GOP skeptics of Bush's plan, including Gordon Smith of Oregon and Sen. Susan Collins of Maine, will agree to Kennedy's plan is doubtful.

"It would be a dishonorable thing for the Congress to budget away the bullets at a time when their commander in chief had ordered them to hold their place in the battlefront," said Smith.

Collins, who recently returned from Iraq, said she remained unconvinced that more troops could help salvage the situation. She said one or two brigades might be needed in the Anbar province, which is showing signs of improvement, but that those forces could be reallocated from elsewhere in the country.