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WASHINGTON -- The nation's health system can't be transformed by rationing medical care, President Barack Obama's new Medicare chief said Monday in his first major speech.

Dr. Donald Berwick's appointment earlier this summer without Senate confirmation was contentious because some Republicans accused him of being willing to deny care to save on costs. Since then, the administration has kept Berwick out of the limelight, turning the otherwise well-known medical innovation guru into something of a mystery man in Washington.

Berwick broke his silence Monday, telling an audience of health insurance industry representatives that pushing back against unsustainable costs cannot and should not involve "withholding from us, or our neighbors, any care that helps" or "harming a hair on any patient's head."

Berwick also said he doesn't think federal bureaucrats have all the answers when it comes to remaking the system. "A massive, topdown, national project is not the way to do this," he told a conference hosted by America's Health Insurance Plans, the industry lobbying group.

Berwick, 64, a pediatrician and Harvard professor before he came to government, has long advocated what he calls "patient-centered care," coordination of services to provide better quality and avoid duplication and waste.

The choice of the insurance lobby for his speech was unusual since the administration continues to trade verbal potshots with the industry. Last week Berwick's immediate boss, Health and Human Services Secretary Kathleen Sebelius, publicly warned insurers not to try to blame rate hikes on the new health overhaul law.

As head of Medicare and Medicaid, Berwick oversees programs that insure more than 80 million Americans, many of them in vulnerable health. The administration wants to use Medicare and Medicaid as laboratories to test the main quality improvement and cost control ideas in the health care law.

These include "medical homes" in which a primary care doctor assumes responsibility for patients' overall health, following up on whether people take their medications and encouraging commonsense prevention, such as exercise.

Another idea is "accountable care organizations," networks of doctors, hospitals, nursing homes and other providers that would figure out themselves how to best allocate resources to provide quality care.

If pilot programs show that these and other ideas hold promise, the HHS secretary can speed their adoption.

Berwick said he wants a "full partnership" with the insurance industry, since tens of millions on Medicare and Medicaid are already getting health care through private insurers. But he also indicated that he'll be tough on those who resist change.

The industry's top lobbyist, Karen Ignagni, responded after the speech, "We intend to work with you to get it right."

Republicans have seized on previous comments from Berwick, such as this one from an interview last year: "The decision is not whether or not we will ration care -- the decision is whether we will ration with our eyes open. And right now, we are doing it blindly."

They say that raises questions about what Berwick really thinks of rationing. Berwick's supporters counter that rationing already takes place, through actions of insurance companies, and all he wants is to bring the medical decision-making process into the open.

Berwick told the insurers that he has three objectives: better care for individuals; better care for groups of people, such as diabetics or the poor; and reducing per capita costs by eliminating waste and duplication.

"I urge lower costs without harming a hair on any patient's head," Berwick said. He left without taking questions from reporters.