(Updates with comment from Rep. Marcy Kaptur)

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WASHINGTON -(Dow Jones)- A top House Democrat on Sunday said his party has rounded up enough votes to approve a health-care overhaul later in the day, but other leading Democrats suggested the vote count remained in flux.

"We've got the votes," Rep. John Larson (D., Conn.), chairman of the House Democratic Caucus, told CNN's "State of the Union." He reiterated that assessment on ABC News's "This Week."

Debbie Wasserman Schultz (D., Fla.), House Democrats' deputy vote-counter, told "Fox News Sunday," however, that the count was "in flux." "We don't have a hard 216 right now," she said, referring to the number of votes required for the House to pass the bill.

Rep. Jim Clyburn (D-S.C.), the House majority whip, said on CBS's "Face the Nation" on Sunday that "we are not going to talk about that 216 number until such time as we get to the floor."

The House plans to vote later Sunday on the bill, which would expand health coverage to millions of uninsured Americans. The bill, a top priority for President Barack Obama and the Democrats, has been tied up in Congress for nearly a year.

Rep. Marcy Kaptur (D., Ohio), who had held back her support out of concern that the Senate measure would ease up on abortion restrictions, now counts herself as a "yes" vote--welcome news for Democratic leaders.

"We received assurances last night that we will work with the administration and (Health and Human Services Secretary Kathleen) Sebelius and the president to assure that existing law is maintained and not to change it any way and to make sure that it applies to this bill," Kaptur said.

Republicans, who oppose the measure, vowed to put up a strong fight on Sunday and later, when the Senate is expected to take up a separate bill that would make revisions to the measure being taken up by the House on Sunday.

"We're going to use every means at our disposal to oppose this government takeover of health care," House Republican Conference Chairman Rep. Mike Pence (R., Ind.) told CNN.

Democrats are resorting on a two-step process to try to pass the health-care bill, after they lost a 60-seat supermajority in the Senate that would have allowed them to prevent any Republican efforts to block the measure.

Under this approach, House Democrats would seek to pass a version of the health-care bill already passed by the Senate. The president would sign that bill into law. Both chambers would then seek to pass a second bill that would revise parts of the original Senate health bill that are opposed by House Democrats. Passage of the second bill would require only a simple majority in each chamber.

Republicans in the House wouldn't be able to stave off passage of the main health-care bill if Democrats can marshal the 216 voted required. But Senate Republicans will have an opportunity to alter, or possibly stop, the second bill.

Sen. John Cornyn (R., Texas), said Republicans planned to challenge on technical grounds a provision in the second bill that would tax expensive health plans. Speaking on "Fox News Sunday," he said that provision was "extraneous" and shouldn't be voted on as part of the reconciliation bill.

He said that if Republicans were to kill that provision, they could "potentially bring down the whole bill" by eliminating a key funding source for the bill. Congressional analysts estimate that the cost of the two bills combined would be $940 billion over a decade.

Some Republicans suggested that they may offer hundreds of amendments to the second bill in the Senate, potentially gridlocking floor debate. Republicans, arguing that the American public doesn't back the health-care bill, also suggested that if the health-care overhaul were to pass, they would use it as a political cudgel against Democrats in the midterm elections in November, and beyond.

"I'd rather be a Republican running against his bill and saying, 'Let's start over,'" Sen. Cornyn said. "This will be the defining issue in November 2010, and if it passes, in 2012 when the president runs for reelection."

Democratic Rep. Wasserman Schultz said the bill would garner strong public support because some of its provisions, such as a prohibition on health insurers' denying coverage for pre-existing illnesses, would provide immediate benefits.

Sen. Cornyn said the battle over the health-care bill, if it passes, would likely to continue for years, with a number of state attorneys general expected to file suit against various provisions in the bill, such as a requirement that every American obtain health insurance.

"There are a lot of people in the states...who will file suit," he said. "This litigation may go on literally for months and years."

-Patrick Yoest contributed to this report

Copyright © 2009 Dow Jones Newswires