U.S. President Barack Obama is continuing his campaign to reform the American health care system.  He is urging the nation's doctors to put aside their skepticism and back changes that he says are needed to bring skyrocketing medical costs under control.

President Obama went before the nation's largest organization of physicians to make the case for health care reform.

"The cost of our health care is a threat to our economy," he said. "It is an escalating burden on our families and businesses.  It is a ticking time bomb for the federal budget.

In a speech to members of the American Medical Association at their annual meeting in Chicago, the president spoke in stark terms.   

He talked about big corporations like General Motors that are in trouble in part because of the high cost of providing health insurance to employees.

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

The president faced a tough audience.  There is consensus in the medical community about the need for reform to improve the affordability and accessibility of quality care.  But there is no unity on the best medicine to heal the ailing system.

The president went out of his way to assure them that he does not support a government take-over.  But he said there needs to be a way to provide health insurance to those of modest means.  And he took on a major concern for doctors: the fear of a malpractice lawsuit.

President Obama said he does not favor limits on the amount of money juries can award in malpractice lawsuits.  But he said he is open to other options, and he pledged to work with the medical community.

"I need your help, doctors, because to most Americans, you are the health care system," he said.

Republican leaders in the U.S. Congress responded to the president's remarks by charging once again that he wants a health care system run by bureaucrats in Washington.