Nov. 10 (Bloomberg) -- Democrats are hardening their stances on both sides of the abortion issue in a battle that may threaten plans to overhaul the U.S. health-care system.

More than 40 party lawmakers vowed to vote against a final bill if it contains language the House agreed to on Nov. 7 adding restrictions on the procedure as part of broader health legislation. The issue may also disrupt work in the Senate, which has yet to unveil a bill.

Abortion “is going to be a major issue,” Illinois Senator Dick Durbin, the No. 2 Senate Democrat, told reporters yesterday. “I hope we can find a way around it”...