GREEN BAY, Wis. — President Barack Obama challenged Republican critics Thursday to offer alternative plans for overhauling U.S. health care, declaring he's "happy to steal people's ideas" but that doing nothing about out-of-reach costs and uninsured Americans is not an option.

"What else do we say to all those families who spend more on health care than on housing or on food?" Obama said at a town hall-style meeting, surrounded by supportive citizens in the nation's heartland. "What do we tell those businesses that are choosing between closing their doors and letting their workers go?"

Undertaking an aggressive new effort to push a major health care measure through Congress by August, Obama rebuked critics from both the right and left — conservatives who say his support for creating a government-sponsored insurance option alongside private coverage would send the country toward an unsustainable nationalized plan, as well as liberals who are concerned he won't go far enough to mandate universal coverage.

Obama said the question of what to do about health coverage, which has vexed Washington for decades, has reached near-emergency status.

"I know there are some who believe that reform is too expensive, but I can assure you that doing nothing will cost us far more in the coming years," Obama said. "Our deficits will be higher. Our premiums will go up. Our wages will be lower, our jobs will be fewer and our businesses will suffer."

There is emerging bipartisan consensus around many big isssues of health reform, including a need to move all Americans toward coverage and to prohibit insurance industry practices that deny coverage to people with health problems.

But there remain major disagreements over how to pay the $1.5 trillion it will cost over the next decade to cover the 50 million Americans who lack coverage, as well as whether employers should be required to offer coverage and whether government-sponsored insurance should be one option.

Obama has detailed few specifics that he is for and against, and he did not break any new ground on Thursday.

But his steadfast support for a public insurance component in any plan is a major obstacle to bipartisan agreement on a final bill.

"We see that as a slippery slope to having the government run everything," Sen. Mike Enzi, R-Wyo., said at a news conference in Washington.

Conservative activists appear to be mobilizing. Several hundred protesters lined the president's brief motorcade from the airport to a suburban high school, holding signs such as "NObama" and "No to Socialism" — a rare occurrence for the popular new president.

Obama says creating the option of a government-sponsored health plan alongside private insurers would increase competition and lower costs. But in answering a question on Thursday, he also said that no one — "certainly not me" — is interested in a nationalized health care system like that in Britain. The president said the government is not going to force any change upon people who are pleased with the plans they already have with their employers.

"When you hear people saying socialized medicine, understand, I don't know anybody in Washington who is proposing that," he said.