AFP - US President Barack Obama's historic drive to extend health insurance to nearly all Americans faced a crucial House of Representatives vote Saturday, with Democrats predicting victory.

A day after Obama and key allies unhesitatingly predicted the sweeping legislation would pass, leading Democratic lawmakers split on whether they had locked down the 216 votes needed but vowed to prevail in the cliffhanger test.

"We don't have a hard 216 right now," Representative Debbie Wasserman Schultz, a top Democratic vote-counter, acknowledged on Fox News television, before insisting the measure would pass.

Representative John Larson, chairman of the House Democratic Caucus, told ABC television: "We have the votes. We are going to make history today."

And Democratic House Majority Leader Steny Hoyer told NBC television "there are still members looking at it, trying to make up their mind" but predicted the legislation would get "216-plus votes when we call the roll."

Republicans, united in opposition to Obama's top domestic goal, vowed to keep up the fight in the House and Senate, and repeal the bill if they win back majorities in the November mid-term elections.

"They don't have the votes yet," Republican House Minority Leader John Boehner told NBC. "This fight is not lost yet."

Related article: Republicans to hit health bill with amendments

The House vote, set for sometime after 2 pm (1800 GMT), was to come after a year of acrimonious debate, bitter partisanship and legislative logjams that threatened the most sweeping overhaul of its kind in four decades.

Obama's plan, a compromise between rival House and Senate versions of the bill passed in late 2009, would bring the world's richest country closer than ever to guaranteeing health care coverage to all of its citizens.

Using a blend of expanded government health programs and subsidies for millions to buy private insurance, the bill would add 32 million Americans to the ranks of those covered for a total of 95 percent of Americans.

The vote on what Obama has called "the toughest insurance reforms in history" would come a century after president Theodore Roosevelt called for a national approach to US health care.

The Democratic plan called for the House to approve the Senate version of the legislation, sending it to Obama to sign into law, then a package of "fixes" to make it more like the House-passed health care bill.

The Senate would then take up the changes and approve them separately, under rules that prevent Republicans from using a parliamentary tactic, the filibuster, to indefinitely delay and therefore kill the measure.

Senate Republicans plan to besiege the legislation with "hundreds of amendments," to "highlight what is in the bill that is bad," one of their leaders, John Cornyn, told Fox News.

They also plan to challenge specific provisions of the bill as not having a direct effect of reducing the deficit, a requirement under the process Democrats have invoked to pass the bill, he said.

Cornyn acknowledged that Vice President Joe Biden, the Senate's presiding officer, could declare the amendments to be purely delaying tactics and call a vote on the legislation.

"I guarantee it will happen on television, on C-Span and on Fox News and for 300 million people to see and I think there will be a terrible price to be paid for this sort of defying public opinion," said Cornyn.

Recent public opinion polls have painted a confusing picture, with respondents expressing strong support for individual elements of the bill, but with large numbers saying they oppose the overall measure.

Democrats have highlighted the independent Congressional Budget Office's estimate that the bill would cost 940 billion dollars over the next 10 years, while cutting 143 billion dollars from the bloated US deficit through 2019 and 1.2 trillion over the following decade.

Obama, who met or spoke to scores of wavering lawmakers this week, led House Democrats in a triumphant rally Saturday and declared himself "confident" they would pass the bill -- while acknowledging a likely political price.

"I know this is a tough vote," he said, before promising "it will end up being the smart thing to do politically because I believe that good policy is good politics."

As Obama spoke, thousands of protestors outside the Capitol chanted "Kill The Bill" and waved signs branding the president and his proposal "socialist" and lawmakers "corrupt."