Many U.S. doctors who care for the nation’s elderly and disabled are likely to stop providing some services and spend less time with patients if Medicare cuts their payments, a physician group’s survey released on Tuesday said.

Congress has established a formula that determines how much doctors can receive for Medicare services such as office visits, tests and certain drugs given in office settings.

Under that formula, physician payments have been slated for cuts, but in the last couple of years lawmakers have stepped in to raise the rates.

An annual government report released last year indicated payments to doctors could drop 5 percent starting in 2006 and the cuts could total 31 percent by 2013, according to the American Medical Association, which conducted the physician survey.

The latest version of the report, released last month, said cuts could reach 26 percent over six years.

At the same time, other estimates show doctors’ costs are expected to grow, in some cases as much as 19 percent.

“Physicians want to serve America’s seniors, but they simply cannot afford to accept an unlimited number of new Medicare patients into their practices if Medicare payments do not keep up with the cost of providing care,” said AMA’s president-elect, Dr. Edward Hill.

This year Congress raised doctors’ rates 1.5 percent, and Hill called on Congress and the Bush administration to prevent future cuts.

Of 5,486 doctors who are AMA members, 57 percent said they would spend less time with Medicare patients and 52 percent said they would refer complex cases if the cuts take place. Nearly half said they would stop providing some services.

Sixty-one percent said they would not buy new medical equipment and 54 percent would not invest in new technology, according to the survey conducted in February and March.

The recent government report pointed to “expected rapid cost increases… as well as substantial increases over time in beneficiary premium changes.”

Medicare officials have said they are concerned about growing costs, which they link to patients seeing doctors more often and undergoing more tests and minor procedures.

Agency spokesman Gary Karr said it was unclear if “higher utilization” of services leads to healthier people and that Medicare wants to work with doctors to find out.

Some members of Congress have called for scrapping the current formula entirely and coming up with a new one, but no changes have been set yet.