Washington ? In a blow to the White House, the Senate’s top Democrat signaled Tuesday that Congress may fail to meet a year-end deadline for passing health care legislation, leaving the measure’s fate to the uncertainties of the 2010 election season.

Majority Leader Harry Reid, D-Nev., spoke as Democratic officials said it could be December before Senate debate begins in earnest on the issue atop President Barack Obama’s domestic agenda, months after senior lawmakers and the White House had hoped. The drive to pass legislation has been plagued for months by divisions within the party’s rank and file.

House leaders, on a somewhat faster track, pointed toward a vote this weekend on a bill to extend coverage to tens of millions who lack it, ban insurance industry practices such as denying coverage because of pre-existing medical conditions and generally slow the rate of growth of medical spending nationwide. The 10-year, $1.2 trillion legislation is estimated to expand coverage to about 96 percent of eligible Americans.

The measure includes an option for consumers to purchase a government insurance plan, an attempt to put pressure on private firms.

While Speaker Nancy Pelosi, D-Calif., and House leaders weighed final changes to their version of the bill, Reid for the first time publicly raised the possibility that lawmakers would not be able to meet their — and Obama’s — self-imposed deadline of completing work on health care by year’s end.

“We’re not going to be bound by any timelines. We need to do the best job we can for the American people,” he said after the weekly closed-door meeting of rank-and-file Democrats.

A few hours later, Reid’s office revised his remarks. “Our goals remain unchanged. We want to get health insurance reform done this year, and we have unprecedented momentum to achieve that. There is no reason why we can’t have a transparent and thorough debate in the Senate and still send a bill to the president by Christmas,” said spokesman Jim Manley.

The Congressional Budget Office is preparing cost estimates of a draft bill Reid completed last week.

Any delay past Obama’s oft-repeated year-end timetable would put the issue off until the 2010 election year and inevitably raise doubts about Democrats’ ability to deliver on behalf of the Obama administration.