President Barack Obama has summoned Congress to enact sweeping healthcare legislation, declaring the "time for bickering is over".
In a nationally televised address, he said the moment had arrived to help millions who had insurance and many more without it.
The US healthcare crisis lay at the core of America's burgeoning deficit, he said, telling lawmakers the nation had been brought to "breaking point".
And he implored them to act. "I am not the first President to take up this cause, but I am determined to be the last... the time for bickering is over," he said.
Obama's speech, to a rare joint session of Congress, comes as his popularity is falling, opposition Republicans are on the attack and his fellow Democrats are divided about what kind of plan to pursue.
The president said the changes he has in mind would cost about $900bn over a decade, "less than we have spent on the Iraq and Afghanistan wars, and less than the tax cuts for the wealthiest few Americans" passed in the 1990s.
While there remain some significant details to be ironed out I believe a broad consensus exists for the aspects of the plan
President Barack Obama
He spoke in favour of an option for the federal government to sell insurance in competition with private industry.
But he said he was open to alternatives that create choices for consumers.
Obama hopes to rejuvenate his flagging push for an overhaul of the $2.5 trillion healthcare system, which has bogged down in Congress amid a flood of criticism.
He said his reforms were aimed at cutting healthcare costs, improving care, regulating insurers to help protect consumers and expanding coverage to more than 46 million uninsured Americans.
He also reiterated his support for a government-run insurance plan - the so-called "public option" - that has drawn strong opposition from critics who say it would harm insurance companies and amount to a government takeover of the industry.
"While there remain some significant details to be ironed out," the president said, "I believe a broad consensus exists for the aspects of the plan: consumer protections for those with insurance, an exchange that allows individuals and small businesses to purchase affordable coverage, and a requirement that people who can afford insurance get insurance."
Obama's success or failure may determine whether he has the political clout to press ahead on issues like climate change, arms control and the Afghanistan war.
Sky News White House Commentator Jon-Christopher Bua said: "Tonight President Obama attempted to take back the reigns of leadership on the health care debate.
Obama tried to refocus the debate on the actual reforms that everyone agrees with and away from the "public option" concept.The President made his case for reform on financial grounds citing that our failure to do so put us at a competitive disadvantage in the world marketplace.
He also made his case on moral grounds, invoking Senator Kennedy's memory, declaring it was part of the American character to provide for our fellow citizens in need.
Obama borrowed from the best of both sides of the aisle to finally present a plan that would appeal to most Americans.
He also may have placed the failure to deliver on health care reform squarely in the laps of his Republicans."