House Republican leaders are expected to release changes to their ObamaCare replacement bill Monday night, part of an effort to secure GOP rank-and-file support ahead of a final vote as early as Thursday, multiple sources tell Fox News.

What the expected changes will be remains unclear. But House Speaker Paul Ryan said Sunday that his team continues to refine the measure.

“We are still having conversations with our members,” the Wisconsin Republican told “Fox News Sunday.” “We are making fine-tuning improvements to the bill to reflect people's concerns, to reflect people's improvements.”

Ryan suggested those changes will be related to increasing tax credits for lower-income and older people and allowing states to impose a work requirement for able-bodied Medicaid recipients and to accept a fixed block grant for Medicaid.

The changes could give governors, not the federal government, the authority to end Medicaid expansion in their states and to change the work requirements on Medicaid.

The changes are expected to be codified in a so-called manager’s amendment, which House Republicans will presumably attach to the final bill that the Rules Committee will review Wednesday, before the final vote.

Ryan expressed confidence Sunday about getting the requisite 218 votes to send the bill, the American Health Care Act, to the GOP-controlled Senate. But whether he can reach that mark remains unclear.

Texas GOP Rep. Kevin Brady, chairman of the House Ways and Means Committee, said some of the changes will be “technical” and “policy” related and will “further strengthen the bill.”

House Republicans are expected to get an updated cost and economic impact analysis from the Congressional Budget Office.

Fox News’ Chad Pergram contributed to this report.