The White House sought to downplay differences on Sunday between the two versions of healthcare legislation passed in Congress as Democrats prepared to meld them into one, while a top Republican saw great unrest and perhaps more party-switchers among Democrats.

The Senate passed its version of healthcare reform, President Barack Obama's top legislative priority, on Thursday with no Republicans voting for it. The House of Representatives passed its bill on November 7 with just one Republican vote.

Democratic lawmakers in early January will begin the tricky task of resolving differences between the two versions, such as whether to keep a new government-run insurance program as the House envisions, how to craft language to restrict abortion funding, and what approach to use to pay for the overhaul.

Republicans vowed to keep battling to block it and expressed hope some Democrats may yet turn against it.

The bill is not law yet, Senate Republican leader Mitch McConnell said on ABC's This Week program, adding that there were rumors of more possible Democratic defections amid unhappiness over the healthcare proposals.

U.S. Representative Parker Griffith of Alabama switched parties on December 22 and became a Republican.

There is great unrest in the Democratic Party, McConnell said. The reason for that is the surveys (opinion polls) indicate the American people are overwhelmingly opposed to have the government take over all of their healthcare.

White House spokesman Robert Gibbs, on NBC's Meet the Press, downplayed differences between the House and Senate bills, calling them virtually identical in key provisions.

The major parts of healthcare reform that the president sought to have enacted as a candidate are now very close to happening, and he thinks the commonality between the two proposals overlaps quite a bit, Gibbs said.

Once Democratic lawmakers craft a single, unified bill, the House and Senate would have to pass it again before Obama can sign it into law. The overhaul would forge the biggest changes in the $2.5 trillion U.S. healthcare system since the 1965 creation of the Medicare government health insurance program for the elderly and disabled.

One possible sticking point in the House-Senate bill is over the so-called public option, the proposed government-run insurance plan to compete with private insurers -- an idea very popular among liberal Democrats. The Senate discarded the idea in its bill, but the House included it.

'I'M ALL FOR IT'

Representative James Clyburn of South Carolina, a member of the House Democratic leadership, said on Sunday he could back a bill with no public option if it still had coverage choices and kept costs in check while making insurance firms compete.

So if we can come up with a process by which these three things can be done, then I'm all for it, Clyburn said on the CBS program Face the Nation.

Whether or not we label it a public option or not is of no consequence. What we want to do is get good, effective results from whatever we put in place, Clyburn added.

The measure would extend health coverage to more than 30 million uninsured, covering 94 percent of all Americans, and halt industry practices like refusing insurance to people with pre-existing medical conditions. Most Americans would be required to have insurance and some subsidies would be offered to help some pay for coverage and create state-based exchanges where the uninsured can compare and shop for plans.

There also are different approaches in the House and Senate versions to financing expanded healthcare. The House bill proposes a 5.4 percent surtax on individuals making more than $500,000 and couples earning more than $1 million a year.

The Senate bill includes a 40 percent excise tax on high cost Cadillac insurance plans among other measures including special fees on insurers, drug companies and medical device makers and a 10 percent tax on indoor tanning services.

McConnell said the Senate bill's impact would be to raise taxes by half a trillion dollars and to raid Medicare.

We don't think you ought to take grandma's Medicare and start a new program for someone else, McConnell added.

On Fox News Sunday, Republican Senator Richard Shelby conceded that Republicans were unlikely to be able to block a final version emerging from House-Senate talks.

I think both of them are bad bills, Shelby said. I hope that something happens that we don't see either one come out of a conference, but I'm afraid we will.