The co-author of a House amendment that would exclude abortion from health care reform says efforts to overhaul the US's health care system will fail if the amendment is removed.

US House Rep. Bart Stupak (D-MI) told Fox News' Fox & Friends that if his contentious amendment is stripped from the House bill, it will lose 15 to 20 pro-life votes in the House, meaning it wouldn't have the votes necessary to pass the House.

"They’re not going to take it out," The Hill quotes Stupak as saying. "If they do, health care will not move forward."

But that claim was immediately disputed by another House representative, Diana DeGette, Democrat of Colorado and co-chair of the Congressional Pro-Choice Caucus, who said that Stupak's math is wrong, because many of those 15 to 20 votes were conservative Democrats who voted in favor of the amendment, but still voted against the health care bill as a whole.

"I think [Stupak] won't have the votes when people explain to those members what exactly the Stupak amendment does," DeGette told ABC News.

Progressive politicians and reproductive-rights advocates have been raising the alarm about the Stupak-Pitts amendment to the House's health care bill. The amendment would deny public subsidies to health insurance plans that cover abortion.

Pro-choice activists say the move could effectively further limit access to abortions if health insurers decide to drop abortion coverage in order to qualify for subsidies. And the lack of coverage could, in turn, discourage doctors from providing abortions.

Pro-life groups, such as the US Catholic church, argue that the amendment is necessary because without it health reform would be tantamount to forcing people to condone abortions just by paying their taxes.

DeGette argued that the Catholic church's involvement in health reform is an encroachment on the separation of church and state.

"Last I heard, we had separation of church and state in this country," she said. "I've got to say that I think the Catholic bishops and all of the other groups shouldn't have input."

Despite an outpouring of anger by many women's groups over the church's push to ensure abortion is not covered under health care reform, the US Conference of Catholic Bishops is standing its ground.

"To limit our teaching or governing to what the state is not interested in would be to betray both the constitution of our country and, much more importantly, the Lord himself," said Cardinal Francis George, as quoted at the Washington Times.

Over the weekend, senior White House adviser David Axelrod said President Obama opposes the Stupak-Pitts amendment.

“The president has said repeatedly, and he said in his speech to Congress, that he doesn’t believe that this bill should change the status quo as it relates to the issue of abortion,” Axelrod told CNN's John King. “He’s going to work with the Senate and the House to try to ensure that at the end of the day the status quo is not changed.”

But, as Politico noted, Axelrod would not say if Obama would veto a health care plan that included the abortion restriction.