The U.S. Senate staggered toward the healthcare finish line on Wednesday, as Republicans used new tactics to delay debate and a Democratic holdout remained uncommitted after meeting President Barack Obama.

With Democrats racing the clock to finish before Christmas, the slow-moving Senate healthcare debate ground to a complete halt for several hours as Republicans forced the reading of a 767-page amendment.

Republican Senator Tom Coburn invoked his right to require an amendment by independent Senator Bernie Sanders be read aloud by a Senate clerk -- a task that dragged on for more than three hours before Sanders pulled his amendment.

Democratic Senator Ben Nelson, a moderate and an abortion rights opponent who remains undecided, said he was still undecided after meeting with Obama. He was studying possible compromise language designed to meet his goal of strengthening a ban on using federal funds to pay for abortions.

Nelson said he was consulting with abortion rights opponents in his home state of Nebraska. I don't know whether to characterize it as progress or not, Nelson, the potential 60th vote for the sweeping measure, said of the language.

Senate Democratic leader Harry Reid has been scrambling to corral the 60 votes needed to overcome Republican procedural hurdles. He has no margin of error as Democrats control exactly 60 votes.

The healthcare bill, Obama's top domestic priority, has been bogged down in the Senate amid disputes among Democrats over costs, plans for a new government-run insurance program and Nelson's abortion concerns. Republicans have been unified in their opposition.

Reid agreed to accommodate moderates like Senator Joe Lieberman, an independent who caucuses with the Democrats, by eliminating proposals for the government-run insurance option and an expansion of the Medicare government health program for the elderly and disabled.

'MY VOTE IS NOT SECURE'

But that angered liberals like Sanders, who said he told Obama and Senate leaders his vote was still up in the air.

I've indicated both to the White House and the Democratic leadership that my vote is not secure at this point, Sanders told Fox Business.

Democratic Senator Mary Landrieu, another moderate who earlier voiced concerns about the bill, told reporters on Wednesday she would vote for it barring any surprise changes.

I am generally happy with where the bill is now and will vote for it barring any significant change, she said.

The Senate bill would extend coverage to 30 million uninsured Americans, provide subsidies to help them pay for the coverage and halt industry practices like refusing insurance to people with pre-existing medical conditions.

In an interview with ABC News, Obama cast the debate in economic terms. He said the costs of Medicare and Medicaid, the government health insurance program for the poor, are on an unsustainable trajectory and if no action is taken the federal government will go bankrupt.

Republicans have vowed to use every available tool to slow the debate. On Wednesday, that included forcing the lengthy reading of the Sanders amendment to create a national health system run by the government that even Sanders admitted had no chance of passing.

Coburn made the move after Democrats rejected his request that all remaining amendments be filed for at least 72 hours and given a cost estimate by budget analysts before being considered. He also asked Democrats to accept his amendment requiring certification that all senators had read the bill and understood it before they voted on it.

Republicans are expected to use the same tactic when Reid introduces an amendment making final adjustments to the bill designed to win the 60 votes he needs, including the change in abortion language and the dropping of the government-run insurance option.

That could jeopardize Democratic plans to pass the bill before the Christmas holiday next week. Cost estimates of the amendment from the non-partisan Congressional Budget Office are expected to be released soon.

The Senate moved to a defense spending bill on Wednesday, but is expected to return to healthcare by the weekend.

Reid must file his amendment and three procedural motions to end the healthcare debate in the Senate by the end of the week, setting off a series of votes that will lead to a vote on final passage. Democratic Senator Max Baucus told reporters a final vote on Christmas Eve was the worst case scenario.

If the Senate passes its bill, it would then be reconciled in early January with a version passed on November 7 by the House of Representatives. Each chamber would have to pass it again before sending it to Obama to sign into law.

House Speaker Nancy Pelosi expressed confidence Congress could pass the final measure before Obama's State of the Union address in late January. But she voiced exasperation with the Senate, saying, We should have had a bill months ago.

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