WASHINGTON - A final push to deliver a sweeping healthcare overhaul to President Barack Obama begins this week as House of Representatives Democratic leaders prepare for difficult negotiations with the Senate.

House Speaker Nancy Pelosi is set to meet on Tuesday with House committee chairmen to map out strategy and set their priorities for landmark healthcare reform legislation that the congressional Democrats hope to deliver to Obama within weeks.

The House passed its healthcare bill on November 7. The Senate passed its bill on December 24. There are some significant differences between the bills that must be ironed out as Democrats merge them into a single bill that the House and Senate would have to pass before sending it to Obama to sign.

Healthcare reform is Obama's top legislative priority. Republicans solidly oppose it and have threatened new procedural roadblocks in the Senate to slow things down.

Negotiations between the House and Senate Democrats must resolve differences between the two bills over abortion funding restrictions, new taxes to pay for the overhaul, and whether to include a new government-run health insurance program.

Democrats hope to secure final congressional passage perhaps before Obama delivers the annual State of the Union address to Congress later this month or in early February.

That would allow Obama and his fellow Democrats to turn to other issues ahead of November's congressional elections in which they will try to protect their majorities in the House and Senate. These include trying to lower the U.S. unemployment rate and to address national security concerns following the botched December 25 bombing attempt aboard a U.S. airliner.

The stakes are high for businesses, the $2.5 trillion U.S. healthcare industry, Democrats and Obama. Businesses that provide coverage to employees have been struggling to cope with steadily rising insurance costs. Polls show that the public is wary of the proposed overhaul and what it could mean for their household budgets and medical coverage.

Democrats are anxious to settle their differences, deliver a major legislative victory to Obama and begin highlighting the benefits of healthcare reform, which aims to rein in rapidly increasing costs and would prohibit insurance companies from excluding people from coverage due to pre-existing conditions.

'AS QUICKLY AS POSSIBLE'

Democratic leaders could bypass a formal conference between the House and the Senate, shutting out Republicans and avoiding potential partisan procedural roadblocks, to work behind closed doors in concert with the White House to strike a compromise.

Millions of Americans are looking forward to new tax credits to help them afford the healthcare coverage and new rules putting patients ahead of insurance companies, said Senate Finance Committee Chairman Max Baucus, who played a major role in writing the Senate version of the bill.

That's exactly what health reform will do and we are eager to get our reform bill to the president's desk as quickly as possible, Baucus added.

Democrats have little room to maneuver as they strive to maintain the 60 votes in the 100-seat Senate and at least 218 in the 435-seat House that are needed to pass the legislation.

I think they will get this done, said Ron Pollack, executive director of Families USA, a healthcare reform advocacy group. There are some difficult issues, for sure, that need to be worked through.

One key difference is over a proposed new government-run insurance program to compete with private insurers. The House bill includes it. The Senate bill does not.

With conservative Democratic Senator Ben Nelson and independent Senator Joe Lieberman threatening to withdraw their support if the final bill includes this so-called public option, the proposal is unlikely to be included.

Democrats also must resolve differences over abortion language. The Senate bill includes a compromise between Nelson, an abortion opponent, and abortion rights supporters that prohibits public money from being used for abortions.

The House bill includes even more restrictive language backed by a bloc of Democrats who have vowed to withhold support from the final bill if it is changed.

There also are large differences over financing of the bill. The House version includes a 5.4 percent surtax on millionaires. The Senate bill includes a tax on high-cost health plans, a provision opposed by labor unions. The Senate bill also increases the Medicare payroll tax on high earners.

There also are a lot of similarities between the House and Senate bills. Both would create exchanges in which people without employer-sponsored coverage as well as small businesses could shop for insurance. The Senate bill calls for state-based exchanges while the House calls for a national exchange.

(Reporting by Donna Smith; Editing by David Alexander and Will Dunham)