"We are not assuming a thing. We are working hard to bring all Democrats together for the 60 votes necessary to proceed to this historic debate," said Dick Durbin of Illinois, the No. 2 Senate Democrat. "I'm hoping that we can muster our ranks."

The nearly $1 trillion, 10-year Senate bill would extend coverage to millions of uninsured Americans, bar insurance company practices like denying coverage to people with medical conditions, and require nearly all individuals to purchase insurance.

Sixty votes are required to clear Saturday's must-pass procedural vote allowing debate to begin, meaning that all 58 Senate Democrats and the two independents that generally vote with them will need to hold together.

There have been just three question marks in recent days: moderate Democratic Sens. Ben Nelson of Nebraska, Mary Landrieu of Louisiana and Blanche Lincoln of Arkansas.

Nelson and Landrieu have made comments suggesting they'd allow debate to begin, focusing the spotlight on Lincoln, who's facing a difficult re-election next year.

Durbin said Friday that Lincoln has informed Majority Leader Harry Reid how she plans to vote. Durbin wouldn't disclose Lincoln's answer and a spokeswoman for Lincoln had no immediate comment, but Democrats are moving ahead with the vote.

"I would say to Sen. Lincoln that I believe most people in Arkansas would be relieved and happy to see health care reform that gives them the peace of mind about the cost of health insurance and the protection of their ability to fight these health insurance companies," Durbin said.

"I think the failure to pass a bill is not good for America, it's not good for any of us in Congress, or those standing for re-election," Durbin said.

Ahead of Saturday's vote Republicans and Democrats spent Friday trading barbs on the Senate floor over the 2,074-page bill. Republicans displayed the Senate bill and the 1,990-page House bill - stacked on top of each other to form a tall pile - to criticize the legislation as an unwarranted government intrusion. Democrats defended their plan and blasted Republicans for not producing a bill of their own.

"These insurance changes will increase costs for millions of Americans," said Sen. Mike Enzi, R-Wyo. "The voices of August are still out there and they know this bill is just more of the same."

Dismissing Republican criticism, Durbin said, "The Republican health care reform bill is zero pages long because it has zero ideas."

The House earlier this month passed its own health overhaul bill on a 220-215 vote. After Saturday's vote senators will leave Washington for a weeklong Thanksgiving recess, and return for a lengthy and unpredictable debate on the measure, with dozens of amendments expected from both sides.

Both the House and Senate bills would set up new purchasing marketplaces called exchanges where self-employed or uninsured individuals and small businesses could shop for insurance, including the choice of a new government insurance plan.

Both pieces of legislation would rely on more than $400 billion in cuts to Medicare over 10 years to pay for them. The Senate would tax high-cost insurance plans, drug companies and elective cosmetic surgery and raise the Medicare payroll tax on income over $200,000 per year for individuals and $250,000 for couples. The House approach would raise income taxes on the highest-earning individuals and households.