Catholic leaders who say they are for health care reform are worried that some provisions in the health care legislation making its way through Congress could put them out of business by mandating abortion services.

"If abortion becomes a basic benefit, if it gets mandated, then that means anyone who doesn't provide abortions becomes a second-class citizen at the very least in the health care system,"said Richard Doerflinger, associate director of the United States Conference of Catholic Bishops Secretariat of Pro-Life Activities.

He and other Catholic leaders say they could be forced out of networks and referral systems they need in order to survive financially.

Last year alone, the nearly 1,000 Catholic hospitals and health care centers in the U.S. served 92 million patients.

The abortion controversy is the latest to strike the health care overhaul debates in a week that has seen Republicans sharpen their attacks and some Democrats start to waver on Obama's top domestic priority.

Rep. Bart Stupak, D-Mich., who opposes abortion, is sponsoring an amendment that would specifically exclude abortion from any government-run health insurance plan. He says courts have ruled that when health care legislation is silent on abortion, it's considered included.

"If we do not put the specific prohibition against abortion and allow a conscience clause for religious and Catholic hospitals and these workers, it would be part of the bill, it would be understood there is no longer a conscience clause, that we can use public funds for abortion, something that we do not want.

Rep. Tim Ryan, an Ohio Democrat who opposes abortion, has joined the effort as well.

"There needs to be a conscience clause in there, and I don't believe there should be any federal funding for abortions either. So we're quite clear on where we stand on that," he said.

Most lawmakers who support abortion rights also support the idea of protecting a medical professional's right to refuse to perform abortions. But some also are open to some federal funding for abortions in the final version of the law.

On Thursday, Rep. Rosa DeLauro, D-Conn., acknowledged that after the bill is passed, it's likely an advisory panel then will decide exactly what benefits will be included.

"I have been a proponent of low-income women being able to access funds for services and my hope is that we move in that direction,"she said. "I know that others are opposed to that. That's why there hasn't been any language put into the bill. It will be when the bill is passed and when we take a look at what benefit levels are."

Although House Speaker Nancy Pelosi continues to say she has the votes to get a health care measure passed in the House, Stupak says unless the abortion issue is resolved, Pelosi will never get enough Democrats on board, and he claims he's got the votes to bring the House debate to a grinding halt.