ANNANDALE, Va. — At an emotional forum in Virginia, President Barack Obama hugged a cancer patient Wednesday and vowed to bring greater efficiency and accessibility to the nation's health care system.

Debby Smith, 53, of Appalachia, Va., fought tears as she told Obama of her kidney cancer and her inability to obtain health insurance or hold a job. The president embraced her and called her "exhibit A" in an unsustainable system that is too expensive and complex for millions of Americans.

"We are going to try to find ways to help you immediately," he told Smith as hundreds watched at a community college forum — and countless others on television. But the nation's long-term needs require a greater emphasis on preventive care and "cost-effective care," he said.

Obama said the best way to drive down health care costs is to persuade doctors and hospitals to emphasize quality of care over the quantity of procedures.

Health experts have long criticized formulas that tie Medicare payments to tests and other services that may not always be the best way to treat a patient. Obama said the formulas must change as part of his bid to overhaul U.S. health care delivery.

"The biggest thing we can do to hold down costs is to change the incentives of a health care system that automatically equates expensive care with better care," the president said. He said the formula system drives up costs "but doesn't make you better."

Obama did not make specific recommendations for changing the incentive formulas. Nor did he offer new proposals or details for other tough issues, such as whether to limit medical malpractice awards or to tax employer-subsidized health care benefits.

He repeatedly said the current health care system is not acceptable and must be overhauled this year. He urged the audience, which included people following on Facebook and YouTube, to reject critics who say his plans are too costly or a step toward socialized medicine.

Obama said a government-run "single-payer" health care system works well in some countries. But it is not appropriate in the United States, he said, because so many people get insurance through their employers working with private companies.

But he again called for a government-run "public option" to compete with private insurers, a plan that many Republicans oppose.

Obama said the public option would provide "competition and choice" and "keep insurers honest."