Abortion opponents in the Senate want tough restrictions in the health care overhaul bill, similar to the limits passed by the House this past weekend.
The issue could roil an already shaky Democratic effort to pass a health care bill by year's end for President Barack Obama.
Democratic Sen. Ben Nelson of Nebraska said Monday it's highly unlikely he would support a bill that doesn't clearly prohibit federal dollars from going to pay for abortions. His spokesman said Nelson is weighing options, including offering an amendment similar to the one passed by the House.
The limits in the House bill have angered liberals, some of whom are now threatening to vote against health care legislation if the curbs stay in.