WASHINGTON – Sexual performance drugs such as Viagra will be covered in Medicare’s new prescription drug program, a lifestyle rather than lifesaving benefit that conservatives and watchdog groups say the government shouldn’t provide.

Like those for maladies such as high blood pressure and heart disease, prescriptions for Viagra and similar drugs in its class will be tightly controlled. The new prescription coverage begins next January 1 and is expected to cost more than $500 billion over the next decade.

“The law says if it’s an FDA-approved drug and it is medically necessary, it has to be covered,” said Gary Karr, spokesman for the Centers for Medicare and Medicaid Services, which administers the health insurance program for older Americans.

Pfizer’s Viagra, Bayer’s Levitra, and Eli Lilly & Co.’s Cialis are used primarily to treat erectile dysfunction, but they also help treat enlarged hearts that can result from high blood pressure.

Some conservatives and public watchdogs say Medicare coverage of sexual performance drugs could bankrupt the program.

“Asking Uncle Sam to pay for the romance of 76 million baby boomers will quicken the impending collapse of Medicare,” said Tom Schatz, president of a taxpayer watchdog group, Citizens Against Government Waste.

“These bureaucrats defend the additional drugs as ‘lifestyle-improving’ instead of ‘just lifesaving,’ but tax-funded Viagra will drain resources from medication for more severe conditions,” Mr. Schatz said.

Mr. Karr said no analysis has been done on the cost of covering prescriptions for sexual performance drugs.

Conservatives say the law puts Congress, and not doctors, in the position of deciding which drugs should be covered – precisely the kind of big-government role that majority Republicans and President Bush campaigned against.

“You cannot have a universal entitlement like this without extreme micromanagement,” said Robert Moffit, a health care analyst at the Heritage Foundation. “Members of Congress, frankly, are not competent to make these decisions,” Mr.Moffit added. “Micromanagement will institutionalize incompetence.”

On Capitol Hill yesterday, talk turned to what types of drugs are covered by the new law. “We’re going to have to take another look at this whole drug benefit,” said Senator Gregg, a Republican of New Hampshire, the new chairman of the Senate Budget Committee.

Since it was approved by the FDA in 1998, about 16 million men have tried Viagra, according to Pfizer.

The Los Angeles Times first reported Medicare’s coverage of sexual performance drugs.