(CNN) Democratic Sen. Joe Manchin is casting skepticism in conversations with senators that the Build Back Better bill can pass the Senate this year, potentially delivering a blow to Senate Majority Leader Chuck Schumer's push to get the bill approved by Christmas, according to two sources familiar with the West Virginia senator's remarks.
Manchin still has a number of concerns, namely that budget gimmicks hide the true cost of the bill, and he's pushing to ensure it costs no more than $1.75 trillion. But he also is seeking to pare down the bill, which passed the House last month, in a number of other areas -- including paid family leave, a methane fee on emissions from energy producers and a Medicare expansion to cover hearing costs. And he's seeking changes to some of the provisions in the tax title of the bill, one of the sources said.
All of that means major changes would need to be made to the bill, followed by a full cost analysis by the Congressional Budget Office, and a review by the Senate parliamentarian, which is raising doubts that could all be accomplished in time for passage by the Christmas, as Schumer hopes.
One Democratic source pegged the likelihood that the bill can pass this year at "20-25%."
"He has a lot of concerns," the source said.
Asked about his private comments to senators, Manchin told CNN on Thursday night that the timing of the vote depends on when the Senate parliamentarian rules on what parts of the bill comply with the chamber's strict rules.
"Debt and inflation are a big concern for me," the West Virginia Democrat said. "Basically we should pay for what we're doing."
Manchin said on Thursday that if Schumer tries to force him to make a decision by putting a bill on the floor, "I wouldn't have any idea how I'm going to vote until I walk in."
If he voted no, as Republicans hope, it would sink the bill in the 50-50 Senate.
Another influential moderate Democrat, Sen. Kyrsten Sinema of Arizona, did not commit to voting for the President's sweeping social safety net legislation in an interview with CNN on Thursday.
Following the passage of the economic bill in the House, Schumer said Senate Democrats would try to negotiate with Manchin and Sinema to address their disagreements on the size and scope of the package.
"The House did a very strong bill. Everyone knows that Manchin and Sinema have their concerns, but we're going to try to negotiate with them and get a very strong, bold bill out of the Senate, which will then go back to the House and pass," Schumer, a New York Democrat, said during a news briefing in late November.