WASHINGTON — In the face of solid Republican opposition, Senate Democrats on Tuesday backed down from their effort to increase Medicare payments to doctors without offsetting any of the cost over the next 10 years. It was the first skirmish in a larger partisan battle over President Obama’s effort to remake the health care system in a fiscally responsible way.

The Senate majority leader, Harry Reid, Democrat of Nevada, had hoped to whisk the Medicare bill through the Senate this week, before taking up a much larger bill to provide health insurance to nearly 30 million Americans.

But Republicans had other ideas, and so did some moderate and conservative Democrats. They said they could not swallow the Medicare bill because it would cost $247 billion over 10 years and none of the cost would be offset or paid for.

Mr. Reid said the bill would “fix” a flawed formula that threatens to cut Medicare payments to doctors by 21 percent in 2010 and by about 5 percent in each of the next few years. If such cuts occurred, he said, fewer doctors would accept Medicare patients.

Republicans support the goal, but want to pay for it.

In the House, Speaker Nancy Pelosi met Tuesday night with the full Democratic Caucus and said she had nearly finished work on a health care bill whose 10-year cost would be less than the $900 billion limit recommended by Mr. Obama. Ms. Pelosi restated her desire to create a “robust” government insurance plan but said she was carefully counting votes and would alter the details if needed to secure House approval.

Doctors have lobbied hard for the Senate Medicare bill, hinting that its passage would inspire them to make an all-out push for a broader health care overhaul.

The Senate Democratic whip, Richard J. Durbin of Illinois, said “it’s frustrating” to see Republicans lined up against the Medicare bill.

Mr. Durbin also offered a blunt description of power politics as practiced in the Senate. “Republicans believe they can derail health care reform by defeating the doctor fix,” he said. “That’s what this is all about.”

Mr. Durbin acknowledged that “we don’t have 60 votes on our side of the aisle” to overcome a Republican filibuster and pass the payment bill. Stymied by Republicans, Democrats said they might have to scale down the bill.

Republicans said Democrats were trying to buy the support of doctors by increasing their Medicare payments. Moreover, Republicans said the $247 billion Medicare bill would violate Mr. Obama’s vow that health care legislation not add “one dime” to the budget deficit.

Senator Bob Corker, Republican of Tennessee, said, “I hope that there will be senators on both sides of the aisle who revolt at the majority leader’s push to purchase the support of physicians by, in essence, creating legislation that puts our country another quarter-trillion dollars in debt.”

The Senate Republican leader, Mitch McConnell of Kentucky, said: “I don’t know of a single person who wants to see reimbursements cut to doctors who treat Medicare patients. But if Congress is going to step in and prevent it, we should not do it by racking up more debt on the government’s credit card.”

Mr. Reid said passage of the bill was essential to ensure that doctors continue taking Medicare patients. “One of the biggest fears of seniors is that their doctors will drop them,” he said.

AARP, which represents older Americans, joined the American Medical Association in lobbying for the 10-year Medicare bill.

The chairman of the Senate Budget Committee, Kent Conrad, Democrat of North Dakota, said he was working on a more modest proposal, which would increase Medicare payments to doctors by one-half of 1 percent in each of the next two years. Mr. Conrad said the cost, $25 billion, would be “fully paid for.”

Doctors said they were not happy with the prospect of another temporary solution and wanted the current Medicare formula repealed.

The House Democratic leader, Representative Steny H. Hoyer of Maryland, said he could not support the $247 billion Senate bill in its current form. Mr. Hoyer said House Democrats wanted to couple it with legislation to reinstate a “pay as you go” mechanism, which would require Congress to offset the cost of new spending on benefit programs like Medicare.

Three Democratic senators — Mr. Reid, Max Baucus of Montana and Christopher J. Dodd of Connecticut — met again Tuesday with White House officials to try to put together a health care overhaul bill, melding measures passed by two Senate committees.