A fight over abortion could complicate Senate action on a sweeping U.S. health care reform bill, as some moderate Democrats on have voiced support for a strict ban on using federal funds to pay for the procedure.

"If it doesn't make it clear that it does not pay for abortion, then I wouldn't support it," Nelson, who has voiced a number of concerns about the proposed health care overhaul, told reporters.

Senate Democratic Leader Harry Reid is struggling to muster the 60 votes needed to advance health care reform in the 100-member chamber and he cannot afford to lose any Democrats over the abortion issue.

"It's an additional complication," said Senate Finance Committee Chairman Max Baucus, whose panel shaped the Senate bill. "We'll work it out. We have to get health care passed this year and we will."

The House included in its health care bill a measure that bars anyone receiving federal subsidies from buying a health policy that covers abortion. A proposed government-run insurance plan, known as the public option, also would be barred from covering abortion.

The health care overhaul, a top domestic priority for President Barack Obama, would bring the biggest changes in the $2.5 trillion U.S. health care system since the creation of the Medicare government health program for the elderly in 1965.

Democratic Senator Kent Conrad, a moderate who backed an abortion provision similar to the House plan during Senate Finance Committee debate on the issue, said "it's very very hard" to work out abortion language.

"All of us have recognized throughout that there are three things that could really bring this (health care reform) down," Conrad said. "One is abortion, the second is people who are here illegally, and the third is the public option."

SENATE VERSION

The bill passed by the Senate Finance Committee would require insurers to keep federal subsidies separate from any funds used to pay for abortion. Backers of that provision say it preserves current federal law that bars the use of federal funds to pay for abortion except in cases of rape, incest or to save the life of the mother.

The House narrowly passed its health care reform bill on Saturday and the tighter restriction on using federal subsidies to purchase policies with abortion coverage was the price abortion-rights Democrats had to pay in order to win passage of the bill.

If the full Senate passes a bill, differences between the House and Senate versions would have to be reconciled before a single reform bill would go to Obama for his signature.

The House language angered supporters of abortion rights and they vowed to push to drop the measure from the bill before it reaches Obama's desk.

White House spokesman Robert Gibbs on Monday declined to weigh in on the controversy.

"We will wait to see what health care reform brings," Gibbs said when asked whether Obama would accept the abortion funding restrictions in the House bill.

Democratic Representative Debbie Wasserman Schultz said on Monday that she thought the Senate would resist the House language.

She said that she and others who support abortion rights would be "pushing very, very hard" to ensure it is not in the final bill. (Additional reporting by John Whitesides; Editing by Eric Beech)