U.S. President Barack Obama has slammed Republican 'distortions' and partisan games in the health care debate, during a speech before a rare joint session of Congress.

"Instead of honest debate, we have seen scare tactics," he said Wednesday night, in a crucial address he had been crafting for several days.

"Some have dug into unyielding ideological camps that offer no hope of compromise. Too many have used this as an opportunity to score short-term political points, even if it robs the country of our opportunity to solve a long-term challenge. And out of this blizzard of charges and counter-charges, confusion has reigned."

Tensions were high in Congress. At one point, the president was even heckled by South Carolina Republican Rep. Joe Wilson, who shouted: "You lie!"

The incident seemed to take House Leader Nancy Pelosi off guard, and she exchanged a glance with Vice President Joe Biden. First Lady Michelle Obama shook her head from side to side.

But Obama told his opponents he is determined to bring about reform to the battered U.S. health care system.

"I am not the first president to take up this cause, but I am determined to be the last," he said. "It has now been nearly a century since Theodore Roosevelt first called for health care reform."

Not only must Obama contend with bitterly partisan Republican opponents, but centrist Democrats conscious of public anxiety about handing the government control of health care.

"The Obama administration had a very rough August," David Mark, of the U.S. political website Politico, told Power Play on Wednesday. "There were many protests at town hall meetings with members of Congress, and there was a lot of discontent in the president's own party."

But about 50 million U.S. citizens do not have health insurance, and ballooning health care costs eat up 20 per cent of the country's gross domestic product.

Jeff Zeleny, a political correspondent for The New York Times, said the majority of Americans want some form of change.

"If there's one bright spot in all of the polling numbers that the White House and others have looked through, it's that most Americans want something to be done with health care," he said.

Republicans have sought to portray Obama as a so-called "socialist" trying to expand government control on their lives, and have attacked the public health care systems of Canada and Britain as broken models.

Supporters of Obama's plan are pushing for a "public option" to private health insurance, meaning a government-operated insurance plan, also known as a "single-payer system" in U.S. political jargon.

"There are those on the left who believe the only way to fix the system is through a single-payer system like Canada's, where we would severely restrict the private insurance market and have the government provide coverage for everybody," Obama said in his speech.

But he also suggested he would be willing to pass health care reform without a public option -- or at least not immediately, suggesting that a public option would kick in if private companies fail to provide insurance to enough Americans.

Another compromise would be setting up non-profit health insurance co-operatives, along with enforcing more regulations on private companies -- such as ending the practice of barring customers with pre-existing health problems.

In trying to reform America's health insurance system, Obama has studied the failed attempt by former president Bill Clinton. Unlike Obama, Clinton pre-wrote his plan before bringing it before Congress, and then tried to push it through.

It never made it to a vote.

Zeleny said that a bill will likely be signed at the end of this calendar year, but it may not include the public option.

"Victory will largely be through what the (Democrats) define it," he said. "Might it be incremental? Perhaps, but even incremental steps, they'll say, will bring coverage to a lot of uninsured Americans."