John McCain proposed an overhaul of the nation's health care system Thursday, aiming to give people more control, encourage greater competition and lower costs.

The Republican presidential candidate's plan contrasts sharply with his Democratic rivals' proposals.

He focuses on expanding access for individuals and families but would not require people to carry health insurance. To varying degrees, Democrats want to make health coverage mandatory.

"The solution, my friends, isn't a one-size-fits-all, big-government takeover of health care," he told the Rotary Club of Des Moines. "It resides where every important social advance has always resided — with the American people themselves, with well-informed American families making practical decisions to address their imperatives for better health and more secure prosperity."

He said of the Democrats, "They promise universal coverage, whatever its cost, and the massive tax increases, mandates and government regulation that it imposes."

His proposal emphasizes payment only for quality medical care, and he challenges doctors to do a better job managing care, hospitals to operate more efficiently, pharmaceutical companies to come up with better drugs and insurance companies to spend more on treatment and less on administrative costs.

McCain added that Americans must work to protect their own health and the health of their children, doing "everything we can to prevent expensive, chronic disease."

His plan calls for:

—Allowing people to buy health insurance nationwide instead of limiting them to in-state companies, and permitting people to buy insurance through any organization or association they choose as well as through their employers or directly from an insurance company.

—Providing tax credits of $2,500 to individuals and $5,000 to families as an incentive to help them buy insurance. All people would get the tax credit even if they get insurance through work or buy it on their own.

—Supporting different methods of delivering care, including walk-in clinics in retail outlets across the country, and developing routes for cheaper generic versions of drugs to enter the U.S. market, including allowing for safe importation of drugs.

Aides acknowledged the plan would take time to implement because of its scope. They billed it as a vision for change he would work toward if elected.

"We don't know the cost," McCain said. "We expect there to be dramatic reductions in costs." He said economic models including choice-in-competition always show savings.

Aides said to help pay for the overhaul McCain would end a provision in the tax code that lets employers deduct the cost of health care from their taxable earnings. Additionally, they said, passing lawsuit limits to eliminate frivolous lawsuits and excessive damage awards would help reduce costs.

"He's going a couple steps down the right path, difficult steps, and I applaud him, but he's not quite gotten there," said Laurence Kotlikoff, an economics professor at Boston University who has consulted with both Republicans and Democrats on health care policy.

Kotlikoff said the amount of the tax credit should be tailored to each individual based on that person's personal health circumstances.

"I give him a B or B-plus on this" — better than the grades he said he would give to McCain's GOP rivals.

Mitt Romney wants the government to help states lower premiums by deregulating their insurance industries. He has distanced himself from a 2006 law he signed as Massachusetts governor that requires all residents to get coverage. He says states should be free to craft the specifics of their own programs.

Rudy Giuliani, the former New York mayor, proposes an income tax deduction of $7,500 per taxpayer to defray insurance costs and a tax credit for poorer workers to supplement Medicaid and employer contributions, as part of "market-driven" expansion of affordable coverage.

Fred Thompson, the former Tennessee senator, has not offered a plan.

Among Democrats, front-runner Hillary Rodham Clinton has proposed universal health care and called for a requirement for businesses to obtain insurance for employees. Former North Carolina Sen. John Edwards is seeking to achieve mandatory universal coverage by 2012, while Illinois Sen. Barack Obama is pushing for employers to share costs of insuring workers and ensure that all children are covered.