Landmark U.S. health care reform legislation appears headed for a Christmas Eve vote after clearing a legislative hurdle early Monday morning.

Shortly after 1 a.m. ET, 58 Democrats and two independents won the first of three procedural votes expected this week in the U.S. Senate.

President Barack Obama called the vote "a big victory for the American people," adding that it will make a "tremendous difference for families, for seniors, for businesses and for the country as a whole."

The Democrats needed support from 60 senators on the procedural measure to thwart unanimous Republican opposition and a threatened filibuster.

Final passage of the bill requires a simple majority, and that vote could come as late as 7 p.m. on Thursday, Christmas Eve.

But the bill still needs to go through the process of reconciliation, in which legislation passed in the House of Representatives is harmonized with the Senate's bill.

There are major differences between the two, including stricter abortion language in the House bill, a new government-run insurance plan in the House bill that's missing from the Senate version, and a tax on high-value insurance plans in the Senate that is strongly opposed by many House Democrats.

Some Democratic senators have warned that the Senate bill is supported by a fragile coalition, and that any major change would threaten its survival.

"It took a lot of work to bring this 60 together, and this 60 is delicately balanced," Independent Senator Joe Lieberman said.

A number of concessions were made to get the 60 senators on board, including the removal of the so-called public health insurance option and of a measure to lower the age for Medicare eligibility. While centrist Democratic senators had opposed those provisions, their removal has upset many liberal Democrats.

The proposed bills, each estimated to cost around $1 trillion US over 10 years, would be paid for by a combination of tax and fee increases and cuts in projected Medicare spending.

The bills would ban insurance companies from denying coverage for those with pre-existing conditions. The legislation would also for the first time make health insurance mandatory for nearly everyone in the U.S., provide subsidies to help low-income people buy it, and induce employers to provide it with tax breaks for small businesses and penalties for larger ones.

The non-partisan Congressional Budget Office has estimated that the Senate bill would cut the U.S. national deficit by $132 billion over the next 10 years.

But Republican critics say that reduction is predicated on a $500-billion cut to Medicare, something that may prove difficult.

Critics have also blasted the legislation, arguing it will raise health care costs and insurance premiums. They argue new legislation will lead to the rationing of health care and hurt quality of overall care.

With files from The Associated Press