A broad healthcare overhaul passed its first crucial test in the U.S. Senate on Monday, with 60 Democrats voting to put President Barack Obama's top legislative priority on a path to passage by Christmas.

In a middle-of-the-night vote in a snowbound U.S. capital, Democrats unanimously backed the first in a series of three procedural motions to cut off debate and move the bill to a final vote by at least Christmas Eve.

We'll get this passed before Christmas and it will be one of the best Christmas presents this Congress has ever given the American people, Democratic Senator Tom Harkin said.

Monday's vote was the first test of whether Democrats could secure the 60 votes needed to overcome unified Republican opposition and muscle healthcare reform through the Senate.

Republicans acknowledged they could not stop the bill, which would spark the biggest changes in the $2.5 trillion U.S. healthcare system since the 1965 creation of the Medicare health program for the elderly.

The impact of this vote will long outlive this one frantic, snowy weekend in Washington, Republican Senate leader Mitch McConnell said. This legislation will reshape our nation, and Americans have already issued their verdict -- they don't want it.

The bitter healthcare debate has consumed the U.S. Congress for months and raised the stakes for Obama, with his political standing and legislative agenda on the line less than a year into his first term.

The Senate cast the vote in a formal roll call, with senators calling out their votes from their desk. Democrats hugged and shook hands in celebration afterward, while Republicans headed home quickly.

Democrats were assured of victory on Saturday after their last holdout, Senator Ben Nelson, agreed to a compromise ensuring federal funds would not be used to pay for abortions and sending extra healthcare money to his home state of Nebraska.

With 60 votes in hand, the only drama in the early Monday vote was whether all of the Democrats would make it through the snow-packed streets of Washington to the Capitol.

'PRAY FOR A NO-SHOW'

What the American people ought to pray is that someone can't make the vote tonight, Republican Senator Tom Coburn said beforehand.

The loss of even one Democrat would sink the plan in the 100-member Senate. Democrats control 60 votes, the exact number needed to overcome united Republican opposition.

If the Senate passes the health bill, it must be reconciled with a version passed by the House of Representatives that has stricter anti-abortion language and a government-run insurance option dropped from the Senate bill to appease moderates.

The merged bill must be passed again by each chamber before it is sent to Obama, but the final measure is unlikely to stray far from the Senate version given the difficulties in winning approval there.

Nelson said he will oppose the combined bill if it changes his abortion deal or reinstates the government-run insurance option, and other Democrats voiced similar concerns.

Significant deviations from the core principles I insisted on in this compromise must remain, or I will withhold my support, Democratic Senator James Webb said.

The Senate bill would require most Americans to have insurance, extend coverage to 30 million uninsured Americans and provide subsidies to help some pay for it.

It would set up exchanges where those who are not covered by work-based policies could choose which plans to buy, and would halt industry practices like refusing insurance to people with pre-existing medical conditions.

Obama has asked the Senate to finish by the end of the year to prevent the issue from spilling into the campaign for November 2010 congressional elections. Opinion polls show the bill losing public support, with majorities now opposed to it.

The vote early on Monday formally cut off debate on an amendment offered on Saturday by Senate Democratic leader Harry Reid that made the final changes needed to win the support of all 60 Democrats.

In addition to the abortion compromise and the jettisoning of the government-run insurance option, the revisions require health insurance plans for large groups to spend at least 85 cents of every dollar on medical costs, potentially crimping their profits.

Also included is an increase in the bill's Medicare payroll tax from 0.5 percent to 0.9 percent on income over $200,000 for individuals and $250,000 for couples.

Democrats hope Republicans will surrender once Democrats prevail in the three procedural test votes that require a 60-vote threshold. The next test vote would be Tuesday morning -- 30 hours after the first one -- and the final one on Wednesday afternoon.

If Republicans insist on using all of their allotted time under Senate rules, they can delay the final vote until late on Christmas Eve. That vote requires only a simple majority.

We are not going to give up after this vote, believe me, Republican Senator John McCain said.

(Editing by Eric Walsh)

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