Q+A: What happens next on U.S. healthcare reform?

WASHINGTON (Reuters) - Now that the U.S. Senate and the House of Representatives have passed their versions of healthcare reform, the two chambers must work out their differences before legislation can be delivered to President Barack Obama for his signature.

Here are some questions and answers about what to expect.

HOW WILL THE BILLS BE MERGED?

Senate and House Democratic leaders, the chairmen of the five congressional committees that wrote the legislation and top White House officials will negotiate the final bill. Most of the discussions are likely to be held behind closed doors whether or not the two chambers appoint a formal conference committee to negotiate the legislation.

Republicans solidly oppose the bill, so the talks will focus on settling differences among liberal and moderate Democrats in a way that wins the needed 60 votes in the Senate and at least 218 in the House.

HOW QUICKLY CAN IT BE DONE?

Since the two chambers are working with similar bills, the final negotiations likely will take a few weeks rather than months. Democrats would like to have a final bill by the time Obama delivers his annual State of the Union address to Congress. Presidents usually give the annual address in late January, but Obama could deliver it in early February, giving more time to congressional Democrats to secure a final deal.

Republicans are likely to resort to procedural tactics in the Senate to slow down final consideration. Democrats will have to wait for a formal cost analysis of the bill by the nonpartisan Congressional Budget Office, a process that can take up to two weeks.

CAN ANYONE KILL THE BILL?

It would be hard for opponents to kill it. The bill is the top legislative priority for Obama. His fellow Democrats are motivated to give him a major victory at the start of his second year in office. Most analysts say the final healthcare bill will be signed into law within the next several weeks despite Republican opposition and efforts to slow it down.

WHAT ARE THE MAJOR STICKING POINTS?

The Senate and House bills are similar in that they set up exchanges in which individuals without employer-sponsored health insurance and small businesses can shop for coverage. Both bills also include major reforms for the insurance industry that would prohibit insurers from excluding people from coverage for pre-existing conditions. Insurers also no longer would be able to base premiums on gender or occupation.

But there are some major differences between the two bills. The House one includes a new government-run insurance program to compete with private insurers. The Senate bill does not include this so-called public option. Leaving it in the final bill could jeopardize Senate passage. Two senators have said they would withdraw support if that provision is included.

Senate and House Democrats also have to work out differences in financing. The House bill relies on a 5.4 percent surtax on millionaires to finance the bill. The Senate includes an increase in the Medicare payroll tax and a tax on high-cost health insurance policies, a provision opposed by labor unions.

WHAT HAPPENS AFTER THE HOUSE AND SENATE REACH AGREEMENT?

Both the House and Senate must pass the final version of the bill before it is sent to Obama for his signature.

Once it is enacted into law, some provisions would go into effect immediately, such as barring insurers from excluding coverage for children due to pre-existing conditions.

Democrats will emphasize the measure's benefits as they try to protect their House and Senate majorities in November congressional elections. Republicans, who stand a good chance of taking some Democratic seats, are expected to stress Medicare spending cuts and tax increases in the bill.

Federal agencies will start writing regulations to implement the overhaul. A provision requiring everyone to purchase healthcare insurance almost certainly will face a court challenge from people who believe the Constitution does not give Congress authority to require everyone to purchase a product from private companies.

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