Senate Budget Chairman Kent Conrad (D-N.D.) and Finance ranking member Chuck Grassley (R-Iowa) are working on a plan to pay for a $245 billion extension in Medicare payments to doctors, hoping to find a way to quell bipartisan Senate opposition.

Senate Majority Leader Harry Reid (D-Nev.) scrapped a planned Monday vote to take up the Medicare extension bill in the face of stiff opposition from Republicans and Democrats who don’t want to move the massive bill without offsets.

The details of the Conrad-Grassley plan are still being worked out. And aides on both sides of the aisle said Monday that it is unclear whether the Conrad-Grassley plan — or any other proposal — will make it into the final legislation. Those aides suggested Reid is likely to oppose any amendments to the “doc fix— measure.

The extension to the Medicare payment program was originally included in the massive health care reform bill now working its way through Congress, but Reid carved the costly provision out, arguing that the extension is needed immediately.

Republicans, however, have accused Democrats of gamesmanship, arguing that moving the Medicare extension as stand-alone legislation allows Democrats to claim the broader health care reform bill will be deficit-neutral.

“It’s perfectly obvious why Democrats want to resolve this issue outside the larger debate over health care. They’re doing it so they can say their health care plan doesn’t add to the deficit. It’s a gimmick, and a transparent one at that,— Minority Leader Mitch McConnell (R-Ky.) said Monday, adding that the GOP will offer amendments to offset the costs of the measure when Reid brings it to the floor.

“Democrats in Congress want to borrow another quarter of a trillion dollars to keep doctors from getting a pay cut. … There are ways to pay for it,— McConnell said. “And when this matter comes before the Senate, Republicans will offer ways to pay for it without asking taxpayers to take on another quarter of a trillion dollars in debt.—

A GOP leadership aide said there are several Republican amendments being worked on that could be offered, including one that would tap unused stimulus funds.

Democrats expressed frustration at the delay Monday, arguing that Republicans were effectively filibustering the legislation even as they claim they support the extension.

“Even Republicans know that compensating doctors fairly is a critical issue. At the Senate Finance markup, Sens. Kyl, Hatch and Grassley all commented on the effect reducing Medicare doctors’ payments would have on seniors’ access to doctors,— Reid spokesman Jim Manley said, referring to GOP Sens. Jon Kyl (Ariz.) and Orrin Hatch (Utah).

Indeed, a Democratic aide accused Republicans of trying to have it both ways — arguing that they agreed to vitiate Monday’s planned cloture vote because they did not want to be seen filibustering the bill.

But a GOP leadership aide rejected those claims, arguing Reid would never avoid a vote that he thought would hurt Republicans. “I love that they would suggest that Harry Reid would pull down a vote for Republicans. … How many votes did we have on Iraq [in 2008], three a month?— the aide asked.

Reid is still expected to try to bring the bill to the floor this week, and leadership aides in both parties said preliminary talks on a narrow set of amendments to the bill have already begun.

Depending on how long the Medicare measure is on the floor, Reid hopes to also clear at least one appropriations conference report this week. Only two of the 12 appropriations bills have made it through a House-Senate conference and to the president’s desk this year, making it a near-certainty that Congress will have to pass another continuing resolution to keep the government operating. The current CR, passed as part of the legislative branch spending bill, expires Oct. 31.

Democrats have also urged Reid to bring up legislation extending unemployment benefits an additional 14 weeks, but that bill has not moved as Republicans look to attach amendments to it. Led by Sen. Johnny Isakson (Ga.), Republicans want to include an extension of the popular tax credit for homebuyers. But Democrats, aware that the Obama administration has been cool to extending the homebuyers credit, are trying to block the effort.