WASHINGTON - Older Americans could see big changes in Medicare as a result of a health-care overhaul, lawmakers and experts said yesterday as Congress began working on the sweeping legislation.

Medicare should become the test lab for making the entire health-care system less wasteful, experts told a receptive Senate Finance Committee. Savings could be used to strengthen Medicare itself, they said, or be plowed into covering the uninsured.

Medicare covers 45 million Americans who are elderly or disabled, and its policies set the tone for many private insurers. The new approach for seniors would stress close follow-up care by their family doctors and nurses. The aim is to keep chronically ill patients from needing repeated hospitalization when such problems as high blood pressure get out of control.

Doctors and hospitals would also see big changes. Primary-care doctors would be paid more. Specialists, who tend to order more tests and procedures, would face closer scrutiny of their decisions. Hospitals could be penalized if patients do not get adequate follow-up care and wind up repeatedly readmitted for the same problems.

Similar changes would be in store for Medicaid, the federal-state partnership that covers 50 million low-income people.

"Medicare is going to be the driver to achieve quality reforms, in large part because the other players tend to follow Medicare," said Finance Committee Chairman Max Baucus (D., Mont). He aims to have a bill on the Senate floor this summer that would restrain costs and cover the 50 million uninsured.

His committee began its work yesterday by hearing from a roundtable of experts and industry representatives on how to revamp health-care delivery. "These roundtable discussions will preview many of the policies that the committee will consider," Baucus said.

The panel will meet next week in closed session to discuss specific options that would become the building blocks for legislation on changes to Medicare and the broader delivery system.

The committee will then turn to coverage and financing, holding both open discussion sessions and closed decision meetings. Baucus hopes to craft a bill that Republicans as well as Democrats can support, but fundamental disagreements exist over the role of government, the responsibilities of individuals and employers, and how to pay for the plan.

Medicare will cost taxpayers about $425 billion this year. Program spending, however, is not evenly divided among beneficiaries. Instead, the sickest 10 percent of the patients account for just under two-thirds of the cost.