WASHINGTON — President Barack Obama pressed his fight for a health care overhaul, using a nationally televised news conference to seek support from the American public on an issue that has become pivotal for his young presidency.

With his popularity dipping and Republicans on the attack, Obama called an evening news conference Wednesday to argue that changes were needed to guarantee health care for the tens of millions of Americans without insurance and for the financial stability of the United States.

Obama stepped to the microphone looking greyer than the man who ran for president and took office in January. In the past six months, he has confronted critical issues including soaring unemployment, wars in Iraq and Afghanistan and a deadline to shut down the Guantanamo Bay detention facility in Cuba.

It is the health care debate, however, that now towers above all others and overwhelmingly dominated the news conference. The United States is the only major industrialized nation that lacks a comprehensive health care plan.

Obama cited examples of Americans whose insurance would not cover cancer treatment or who went into debt after emergency surgery.

"This debate is not a game for these Americans, and they cannot afford to wait for reform any longer," he said.

On Thursday in the Midwestern state of Ohio, Obama has planned more events focused on health care. He will visit the Cleveland Clinic, which he has praised as a model for reform because it pays doctors a fixed salary that does not depend on how many procedures or tests they perform.

"They've set up a system where patient care is the No. 1 concern, not bureaucracy, what forms have to be filled out, 'what do we get reimbursed for,'" Obama said.

The stakes are huge for Obama, who is putting much of his credibility on the line to gain passage of legislation. At least one Republican said it could prove to be the president's Waterloo if the drive collapses.

Obama has argued that making health coverage affordable and sustainable is so vital that anything less will erode the economic stability of families, businesses and even the government.

He noted that Americans "spend much more on health care than any other nation but aren't any healthier for it."

He wants Congress to vote on comprehensive health care bills before lawmakers break for summer recess in August. That timetable is growing tenuous, though.

Republicans contend Obama's push and emerging congressional bills are rushed and risky, and some conservative members of the president's own Democratic Party are balking as well. A nervous public is being hit by TV ads and claims from all sides.

The top Republican in the House of Representatives, John Boehner, said of the health care legislation: "Mr. President, it's time to scrap this bill. Let's start over in a bipartisan way."

Instead, Obama has been stepping up the fight. He has been seemingly everywhere talking health care: giving statements from the White House, visiting health clinics, talking to bloggers, granting interviews.

The health care debate may have dented Obama's popularity. His approval rating stands at 55 per cent, according to a new Associated Press-GfK poll, down from 64 per cent in late May and early June. Some 50 per cent approve his handling of health care, but 43 per cent disapprove, and that number has risen sharply since April.

It did not help the White House when the nonpartisan Congressional Budget Office said last week that the bills moving through Congress would add to long-term U.S. costs, not reduce them.

Obama said the biggest forces behind the deficit are the rapidly growing costs of government health programs for the poor and elderly, known as Medicaid and Medicare.

Unless they are tamed, he said, "we will not be able to control our deficit."

Obama has said the country is moving in the right direction, and he points to legislation from his first half-year in office including a massive economic stimulus bill that is ultimately designed to work over two years.

"As a result of the action we took in those first weeks, we have been able to pull our economy back from the brink," he said.

Still, unemployment is at 9.5 per cent and rising. Talk that Obama inherited an economic mess from George W. Bush is fading, and the American public is now grading the new president. His approval rating on handling the economy has been slipping as impatience grows.

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