The basic Medicare premium will rise next year to $93.50 a month, an increase of $5 a month, the Bush administration announced Tuesday, but for the first time, higher-income beneficiaries will be required to pay a surcharge.

The standard premium is lower than expected. In May and again in July, Medicare officials estimated that it would be about $98 a month in 2007.

Dr. Mark B. McClellan, administrator of the federal Centers for Medicare and Medicaid Services, said that Medicare spending for doctors’ services, while still growing at a brisk pace, had increased less than expected.

The premium in question is for Part B of Medicare, a voluntary program that covers doctors’ services, diagnostic tests and outpatient hospital care for 40 million people who are 65 and older or disabled. It shot up 50 percent from 2003 to 2006, when it reached $88.50 a month.

Explaining the increase for 2007, Dr. McClellan reported “a modest slowdown in physician spending growth,” but “very rapid growth in spending for hospital outpatient services.”

The surcharge, to be phased in over the three years, is a major change: the first time that high-income beneficiaries will have higher premiums for Medicare coverage. It will ranging from $12.50 to $68.60 a month and is expected to raise $7.7 billion in the first five years and $20.8 billion in the coming decade.

Dr. McClellan said the surcharge would have “a very positive impact, making Medicare more sustainable in the long term.” He dismissed concerns that the higher premiums would prompt some wealthy people to drop out of Medicare, leaving the program to serve poorer, sicker people.

Federal health officials estimate that 1.5 million people — about 4 percent of those in Part B of Medicare — will have to pay the new surcharge, based on income. Because of the surcharge, officials estimate, 9,000 people will drop out of Part B in 2007, and 30,000 will drop out in 2009.

The new surcharge will apply to individuals with incomes of more than $80,000 and married couples filing joint returns with incomes of more than $160,000.

In 2007, the surcharge will be $12.50 a month for a single person with income of $80,000 to $100,000, and the same amount for each member of a couple with combined income of $160,000 to $200,000. Their premiums will total $106 a month.

The surcharge rises with income. An individual with income greater than $200,000 and each member of a couple with combined income of more than $400,000 will have to pay a surcharge of $68.60 a month, for a total premium of $162.10.