Democratic leaders appear confident they have the votes needed to pass Barack Obama's landmark healthcare legislation on Sunday, a day after the president called on them to make history by bringing health insurance to millions of struggling families.

On Saturday, Democratic leaders frenetically hunted for votes inside the Capitol as angry protesters gathered outside, with some hurling racial insults at black members of Congress.

Mr Obama can rely only on Democrats to gain passage of his top domestic priority in a make-or-break vote for his presidency. He faces unanimous opposition from Republicans, who say the plan amounts to a government takeover of healthcare that will lead to higher deficits and taxes.

Some moderate House Democrats also are wary about the plan's costs and abortion provisions.

"I know this is a tough vote," the president told House Democrats at a meeting on Capitol Hill, adding he also believes "it will end up being the smart thing to do politically".

"It is in your hands," Mr Obama said, bringing politicians to their feet. "It is time to pass healthcare reform for America and I am confident that you are going to do it tomorrow."

The US is the only developed nation not to offer its citizens comprehensive healthcare, with nearly 50 million Americans uninsured.

Although the Bill before Congress does not provide universal healthcare, it should expand coverage to about 95% of Americans. It would require most Americans to carry insurance with subsidies for those who can't afford it, expand the government-run Medicaid programme for the poor and create new places to buy healthcare.

Even so, the reform is likely to be judged alongside the boldest acts of presidents and Congress in domestic affairs. While national healthcare has long been a goal of politicians and presidents stretching back decades, it has proved elusive, in part because self-reliance and suspicion of a strong central government remain strong in the US.

It may still elude Mr Obama, too. A series of last-minute flare-ups threatened to slow the Democrats' march to passage, after more than a year of gruelling effort and a turbulent debate that has left the country deeply divided.