Congress has only been able to move on bipartisan Medicare payment reform by mostly ducking the problem of funding it, but Senate conservatives might get a chance to vote their disapproval.

Aides say Senate leadership is considering allowing votes Tuesday on six amendments to the bill repealing and replacing Medicare's flawed physician payment formula — three from Democrats and three from Republicans.

The only one of those amendments that could be passed with a simple majority instead of 60 votes would require Congress to fully pay for the legislation, which replaces the Sustainable Growth Rate formula. It's offered by Sen. Mike Lee, R-Utah.

Despite the 51-vote threshold, there's no guarantee Lee's amendment would pass. Bipartisan leaders in the House and Senate have already agreed to fund just one-third of the bill, and they're eager to get it passed this week in time to avoid big Medicare cuts to doctors.

If the Lee amendment did pass, it would likely alienate some Democrats but win over about 30 conservatives in the House who voted against the bill on the grounds it wasn't completely paid for.

The bill "would likely have significant support from conservatives if it were amended to require its spending to be fully offset," said one senior House aide.

For years Congress has tried and failed to replace the sustainable growth rate, which annually threatens to plunge doctors payments if not overridden with what's known as a "doc fix." Now it's closer to fixing the problem than ever before, with the Senate taking up a reform bill this week the House passed last month.

Congress has until Wednesday to approve a final bill, before the federal government must start enacting the payment cuts.

Besides the Lee amendment, Senate leaders will likely allow votes on five other amendments, including measures from Democrats to extend the Children's Health Insurance Program by four years instead of just two and stripping out language restricting federal funds from being used for abortions.

Another amendment, offered by Republican Sen. John Cornyn, would repeal the Affordable Care Act's individual mandate.