The House's healthcare reform bill will have to be changed before it can even win a majority among Democrats, one centrist, Blue Dog Democrat insisted Friday.

Rep. Jason Altmire (D-Pa.), who opposed the health bill on the Ways and Means committee, signaled that Democrats may not even have the votes to force through a preliminary health bill without any Republican support.

"And in order to get a majority even among the Democratic Party, we're going to have to change the way that House bill is formatted right now," Altmire said during an appearance on Fox News.

Those words come after liberal Democrats strongly signaled to President Obama earlier this week that a publicly available health plan would be essential to winning their votes. House Speaker Nancy Pelosi (D-Calif.) said Thursday that she wouldn't be able to pass a bill without a public option.

Altmire said there would need to be differences of opinion resolved within the Democratic caucus on the health bill before the legislation moves forward.

"There is a difference of opinion on a lot of issues," he said. "These are not insignificant issues, and there are differences of opinion."

The Pennsylvania Democrat said that he's still hopeful a health bill will pass by the end of the year, but said the Congressional Budget Office (CBO) would need to offer a much more favorable assessment of the bill's fiscal impact before it wins his vote.

"Until I see some third-party validation through the CBO and others that the bills that we're going to be called to vote on actually bring down the cost of healthcare and restrain the rate of growth, I'm not going to be able to support it." Altmire explained.