By Susan Cornwell
WASHINGTON (Reuters) - Conservative objections over spending are raising doubts over whether the U.S. Senate can quickly approve legislation fixing the Medicare physician payment system, in a possible setback for Republicans keen to show they can get things done.
Some Senate conservatives are threatening to insist that the measure be fully paid for, after the House of Representatives passed a version of the "doc fix" bill two weeks ago that would expand the federal deficit.
Senate procedural rules confer more power on individual lawmakers, meaning their objections could result in considerable delay and amendments to the bill even if they are in a minority.
The House bill was a rare show of bipartisan accord, and had been shaping up to be the 2015-2016 Republican-controlled Congress' first substantial achievement.
As approved by the House, the $214 billion initiative would replace a 1990s formula that linked Medicare doctors' reimbursements to economic growth with a new one more focused on quality of care.
Republican Speaker John Boehner and Democratic Leader Nancy Pelosi leaned across the aisle to get it passed overwhelmingly in the House of Representatives on March 26, just before a spring break. Senate leaders said they would take it up quickly after lawmakers return to Washington on Monday.
But Senate conservatives, such as Republican Jeff Sessions, have labeled the House bill irresponsible because it would add an estimated $141 billion to the U.S. debt over the next 10 years, according to the Congressional Budget Office (CBO).
The CBO also said that the bill could produce small net savings in the second decade, compared to freezing doctors' reimbursement rates where they are now.
But the conservatives also point to an analysis by an outside budget group -- the non-partisan Committee for a Responsible Federal Budget -- that says the bill would add a whopping half-trillion dollars to the deficit over 20 years.
"I'd like to figure out a way to pay for it," Republican Senator Mike Lee told Reuters on Friday.
Lee is expected to offer an amendment to require Congress to find a way to pay for the "doc fix" by the end of this year.
The conservative group Heritage Action for America, which opposes the bill, is urging senators to strike an exemption from congressional "pay as you go" rules that was written into the House-passed legislation.
Striking the exemption would require Congress to enact enough savings to cover the bill's cost by the end of 2015.
One of the government's largest social safety net programs, Medicare is health insurance that serves 54 million elderly and disabled people.
House Speaker John Boehner on Friday urged lawmakers to see the bill as a conservative gain. The measure requires more means-testing of Medicare beneficiaries so that those with higher incomes pay higher premiums.
"This bill represents the first real entitlement reform in nearly two decades, and CBO and other experts have confirmed that it will save taxpayer dollars over the long term," Boehner said in an emailed statement.
Any significant delay by the Senate would trigger sharp cuts in reimbursements to doctors who participate in the Medicare program for the elderly. The federal government warned Congress last week that it must act before April 15 or thousands of Medicare doctors nationwide will face a 21 percent pay cut under the old reimbursement formula.
However, Senator Ron Wyden, the ranking Democrat on the Finance Committee, said on Thursday that the doctors would be paid in full later at the new rate once the bill passes, because as written the measure is retroactive to April 1.
Senate Democrats may also seek to amend the measure. It includes a two-year extension of the Children's Health Insurance Program (CHIP) for low-income children, but Senate Democrats would prefer this to be four years.
Any Senate change in the bill would also send it back to the House, signaling further delay.