Proclaiming the biggest change in Medicare's history, President Clinton unveiled new protections Tuesday for the health-care program's 38 million beneficiaries.

The new rules require health plans to guarantee that Medicare patients have access to specialists, keep medical records confidential and provide interpreters to those who need them. The rules are scheduled to be published Friday and take effect 30 days later.Clinton hoped his action would prod Congress to approve legislation guaranteeing such rights to all Americans. "This marks the most significant change in Medicare in three decades. It shows what we can do when we put progress over partisanship," Clinton said. He made the announcement Tuesday in the Rose Garden, where he also signed food stamp legislation.

The Medicare regulations - intended to set "uniform national performance standards" - are tighter than those governing private health insurance companies in many states. Congress agreed to most of the new protections as part of last year's balanced-budget act, which also cleared the way for a wider variety of private health plans to serve the elderly starting next year.

Switching to a private plan won't be mandatory, but officials predict that by 2005, 30 percent of all Medicare beneficiaries will choose to join one.

Now, most senior citizens just have their medical bills sent directly to Medicare, which pays them one by one. Lawmakers think Medicare can save money by instead paying a fixed price to insurance companies willing to take on the financial risk that some people will need more care than others.

Among other provisions, the rules allow women beneficiaries to demand "direct access to a women's health specialist" for routine services like Pap smears and breast and pelvic exams.

Patients with complicated problems must also be permitted to go directly to specialists in some circumstances, and a health plan must rule on a patient's request for services within 14 days in most cases or 72 hours in urgent cases.

The new rules also require health-care plans to provide services "in a culturally competent manner" to all Medicare patients, including those with limited English or reading skills.

Medicare beneficiaries will also be entitled to review their own medical records, keep them confidential and obtain financial information about their health providers.

Under the new rules, health maintenance organizations must pay for the treatment of any condition that "a prudent lay person" would regard as an emergency. Medicare beneficiaries also may not be charged more than $50 for any emergency room services.

Candace K. Schaller, a vice president of the American Association of Health Plans, which represents the managed-care industry, said the new requirements were "generally reasonable" but cautioned that plans might need more flexibility on some issues.