WASHINGTON -- After weeks of closed-door negotiations, U.S. Senate Democratic leader Harry Reid plans to unveil broad healthcare reform legislation on Wednesday with a first test vote on the package possible by the weekend.

The healthcare overhaul, President Barack Obama's top domestic priority, has been stalled in the Senate as Reid waited for cost estimates and searched for a way to win the 60 votes needed to clear Republican procedural hurdles.

Senate Democrats have scheduled a 5 p.m. EST meeting to hear details of the bill and get the cost estimates provided by the nonpartisan Congressional Budget Office.

Vice President Joe Biden visited Reid at the Capitol to hear an update ahead of the release of the bill, which would require individuals to buy health insurance coverage and provide subsidies to help low-income Americans pay for it.

The bill merges two health measures passed earlier this year by Senate committees. It would expand coverage to tens of millions of uninsured Americans and halt practices like denying coverage to individuals with pre-existing conditions.

The publication would clear the way for a Senate vote on Friday or Saturday on whether to begin debate -- the first key procedural hurdle for the Senate plan.

Reid said he was "cautiously optimistic" he can win the 60 votes needed to begin the debate, but Democrats have no margin for error -- they control exactly 60 seats in the 100-member Senate and Republicans so far are united in opposition.

A handful of centrist Democrats have rebelled at Reid's decision to include a new government-run public insurance program in the bill, but Reid has been working to corral their support at least to start debate.

If the Senate takes up the bill, the debate is expected to begin on November 30, after the U.S. Thanksgiving holiday next week, and last for at least three weeks.

If the Senate passes a bill, any differences with the version passed by the House of Representatives would have to be reconciled before the final versions can be voted on again in both houses and, if passed, sent to Obama for his signature.

BIGGEST CHANGES IN DECADES

Like the measure approved on November 7 in the House, the sweeping overhaul would spark the biggest changes in the $2.5 trillion U.S. healthcare system since the creation of the Medicare government health program for the elderly in 1965.

The price tag is expected to come in near Obama's goal of $900 billion over 10 years, but Republicans have condemned the bill as a costly government intrusion in the private healthcare sector that would drive up insurance premiums and add to the budget deficit.

Reid already made his toughest decision in merging the two existing Senate bills by promising to include a national government-run public insurance option that would allow states to decline to participate.

He also is considering scaling back a tax on high-cost insurance plans, and including an increase in the Medicare payroll tax on high-income workers to help pay for the subsidies. The tax is the primary source of financing for Medicare, the health insurance program for the elderly.

The bill is not expected to include a mandate that most employers offer insurance to workers or pay a penalty, which was included in the House bill.

Obama has urged Congress to finish its healthcare work by the end of the year to prevent the issue from becoming entangled in the 2010 congressional elections, when all House members and one-third of the 100 senators face re-election.

But Republicans have vowed to drag out the process in hopes it will allow more time for public opposition to mount, as it did in August when lawmakers went home for a one-month recess and faced sometimes fierce criticism from voters.

But Senate leaders have acknowledged it will be tough to complete work by the end of the year.