Washington (CNN) -- Senate Democrat Blanche Lincoln of Arkansas said Saturday she will support bringing the Senate health care reform bill to the floor for debate, giving Democrats the 60 votes they need to prevent a Republican filibuster.
"Although I don't agree with everything in this bill, I believe it is important to begin this debate," she said.
"This issue is very complex. There is no easy fix," she said in making her announcement on the Senate floor, just hours before Saturday night's 8 p.m. procedural vote.
Earlier Saturday, Sen. Mary Landrieu, D-Louisiana, became the 59th lawmaker to agree to vote for debate.
But she added a caveat on the floor of the Senate: "My vote today to move forward on this important debate should in no way be construed by the supporters of this current framework as an indication of how I might vote as this debate comes to an end.
"It is a vote to move forward to continue the good and essential and important and imperative work that is under way."
Sixty votes are needed to move the controversial bill to the floor for discussion. The legislative body is expected to vote Saturday night.
Senate Majority Leader Harry Reid introduced the Senate version of the health care bill on Wednesday. The House passed its version two weeks ago.
Video: Speaking against health bill 
Video: 'This is a defining moment' 
Video: Scrambling for 60 votes Reid says the 2,074-page bill would expand health insurance coverage to 30 million more Americans at an estimated cost of $849 billion over 10 years.
Proceedings got under way shortly before 10 a.m. Saturday and will last through the early evening.
Around 8 p.m., the Senate will hold a roll call vote on the motion to invoke cloture.
Reid needs 60 votes to overcome a certain GOP filibuster attempt and open the chamber's debate on the bill. It also would take 60 votes to close debate that could last for weeks, while final approval of the bill would require only a simple majority.
Sen. Dick Durbin, the No. 2 Democrat in the Senate, said it would be a "real break" if even one Republican got on board with Democrats.
Three moderate Democrats -- Landrieu, Lincoln and Ben Nelson of Nebraska -- had kept party leaders guessing.
Reid met Wednesday with the three, who have expressed concerns about the cost and scope of health care reform proposals.
Read the health care bill (PDF)
Landrieu says she's concerned about the bill's costs to small businesses and individuals, and says she's opposed to a public health insurance option "that will undermine the private insurance market."
On Friday, though, Nelson came out in favor of opening debate.
"Throughout my Senate career, I have consistently rejected efforts to obstruct," he said in a statement. "That's what the vote on the motion to proceed is all about. It is not for or against the new Senate health care bill released Wednesday. It is only to begin debate and an opportunity to make improvements. If you don't like a bill, why block your own opportunity to amend it?"
The Nebraska Democrat had sounded a positive note Thursday after emerging from a meeting with Reid, although he told CNN then that he was withholding his final decision on the motion to proceed until he had a chance to "study [the bill] or at least review it to begin with."
He said there had been concerns about the length of time the bill would be made public before the final vote and whether it would be read on the floor. But it appeared that Reid had largely satisfied his concerns about those issues.
Nelson also said the meeting did not include discussion of the specifics regarding abortion language, the antitrust exemption for the insurance industry and other issues of concern to him.
Lincoln will play a pivotal role in the success or failure of health care reform in the Senate. If Republicans stay unified in opposition to the bill, Reid would need the support of all 58 Senate Democrats as well as independent Sens. Bernie Sanders of Vermont and Joe Lieberman of Connecticut to overcome a filibuster.
The legislative game is just beginning. Expect several weeks of amendments being introduced, impassioned debates on the Senate floor and news conferences for and against the proceedings.
If the Senate manages to pass a bill, a congressional conference committee would need to merge the House and Senate proposals into a consensus version requiring final approval from each chamber before moving to President Obama's desk to be signed into law.
CNN's Ted Barrett, Dana Bash and Evan Glass contributed to this report.
Loading weather data ...
© 2009 Cable News Network. Turner Broadcasting System, Inc. All Rights Reserved.
