CHICAGO (AP) -- President Barack Obama bluntly told doctors Monday he is against their highest legislative priority -- limiting malpractice awards -- and earned a smattering of boos from an audience he was here to court for his health care overhaul plans.

Pushing anew to reshape the nation's health care delivery system and extend coverage to the millions who don't have it, Obama went before the annual meeting of the American Medical Association and took on others who take issue with parts of his plan as well.

Calling them "naysayers," "fear-mongers" and peddlers of "Trojan horse" falsehoods, Obama warned interest groups, lobbyists and others against using "fear tactics to paint any effort to achieve reform as an attempt to socialize medicine."

"There are those who will try and scuttle this opportunity no matter what," Obama said.

GOP Rep. Tom Price of Georgia -- a former orthopedic surgeon -- reacted preemptively to Obama's speech by accusing him of seeking a "government takeover" of health care. Speaking to reporters on a conference call organized by the Republican National Committee, Price said a committee that Obama's administration has established to study the effectiveness of various medical treatments would turn into a "rationing board" to overrule doctors and deny patients care.

And Sen. Jon Kyl, R-Ariz., and other Republicans introduced legislation to ban the rationing of care on such a basis.

The economic stimulus legislation that passed over the winter provides funding for "comparative effectiveness research," and the GOP proposal would block the government from using the results to "deny coverage of an item or service" in a federal health care program.

Addressing the doctors in Chicago, the president said for the first time publicly that health care reform, including covering the almost 50 million Americans who have no insurance, would cost about $1 trillion over 10 years.

"That's real money, even in Washington," he said. "But remember: That's less than we are projected to have spent on the war in Iraq. And also remember: Failing to reform our health care system in a way that genuinely reduces cost growth will cost us trillions of dollars more in lost economic growth and lower wages."

Aides had said previously that the administration wants to keep the cost around $1 trillion, while also acknowledging it might go higher.

Obama has taken steps in recent days to outline where money could be found.

He wants to cut federal payments to hospitals by about $200 billion and cut $313 billion from Medicare and Medicaid over 10 years. He also is proposing a $635 billion in tax increases and spending cuts in the health care system as a "down payment" for his plan.

The president traveled to Chicago to talk to the 250,000-physician group in hopes of persuading doctors not to fight him on reform. The nation's doctors, like many other groups, are divided over the president's proposals. Many are skeptical of his plan to create government-sponsored insurance as an option alongside private coverage.

They also want limits on jury awards in medical malpractice lawsuits -- caps that Democrats, including Obama, have long opposed and Republicans led by former President George W. Bush long pushed for.

Obama drew hearty applause with a focus on the particular concerns of the medical profession: telling them any system that relies on them "to be bean-counters and paper-pushers" is out of whack and that his push to investigate best-practices and eliminate unnecessary procedures "is not about dictating what kind of care should be provided."

"I need your help, doctors," he said. "To most Americans, you are the health care system. The fact is, Americans -- and I include myself, Michelle, and our kids in this -- we just do what you tell us to do."

But the malpractice issue is the most provocative with this audience, which chafes at the heavy expense of malpractice insurance.

Obama started by sympathizing with doctors "who feel like they are constantly looking over their shoulder for fear of lawsuits" and said he recognizes any health overhaul will be hard to accomplish without changing that. The crowd burst into loud support.

"Don't get too excited yet. ... Just hold onto your horses here, guys," Obama said as he prepared to deliver what he knew would be disappointing news.

"I want to be honest with you. I'm not advocating caps on malpractice awards," the president said, greeted by a smattering of boos, a remarkable public response to a popular president accustomed to cheering audiences.

He added, without offering specifics, that "excessive defensive medicine" that is conducted out of fear of lawsuits and that increases health costs should be curbed.

Though he offered no support for limiting lawsuits, Obama raised the antennae of trial lawyers' groups just by mentioning the issue.

The Center for Justice and Democracy, which says it advocates for injured consumers, attorneys and others, released a letter to Obama signed by 64 survivors of medical malpractice saying they were "extremely concerned that the rights of medical malpractice patients may be stripped away as part of your national health care proposal."

"The notion that 'defensive medicine' is leading to higher health care costs is not supported by empirical data or academic literature," Les Weisbrod, president of the American Association for Justice, the main lobby for trial lawyers.

Obama co-sponsored legislation with Hillary Rodham Clinton when both were in the Senate in 2005 that would have created a program to allow patients to learn of medical errors and establish negotiated compensation with the offer of an apology.

The president directly took on criticism from former Republican presidential candidate Mitt Romney, though not by name. On Sunday, Romney, widely expected to consider another run at the White House in 2012, called Obama's support for public insurance a "Trojan horse" to create a single-payer system like Britain's.

"When you hear the naysayers claim that I'm trying to bring about government-run health care, know this: They are not telling the truth," Obama said.

The president repeated that he is "open" to a mandate requiring all Americans to have health insurance. But he said that any plan must address the rising costs of a system he called a "ticking time bomb" for the federal budget.

"A big part of what led General Motors and Chrysler into trouble," he said, "were the huge costs they racked up providing health care for their workers -- costs that made them less profitable and less competitive with automakers around the world."

"If we do not fix our health care system," Obama said, "America may go the way of GM -- paying more, getting less, and going broke."

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