The lower house of the US Congress is debating a historic healthcare reform bill that could lead to tens of millions of uninsured Americans gaining health insurance.

The House of Representatives is set to vote on the legislation late on Saturday or early on Sunday morning.

Barack Obama, the president, on Saturday urged fellow Democrats to support the broadest healthcare reforms in 50 years and his top domestic priority and a campaign promise.

"This is our moment to deliver. I urge members of congress to rise to this moment, answer the call of history and vote yes for health insurance reform for America," he said in a speech from the White House Rose Garden.

Obama also visited congress for a closed-door meeting to encourage Democrats to unite.

'Making history'

The bill stipulates that all Americans have to obtain health insurance or pay a fine, extending it to 36 million more people.

It would create a new government health insurance plan to compete with private insurers, and if passed it would bar insurers from excluding people for so called pre-existing conditions and for charging more based on medical history.

The Democrats have a majority in the House of 258 seats, 40 more than the threshold needed to pass the bill, most of whom have argued that there is a moral imperative to it being passed.

"We will pass health care reform ... We will be making history with our vote," Nancy Pelosi, the Democrat House Speaker, said.

Republicans have been united in their opposition to the bill and have said that if it is passed it will open the door for an expensive government take-over of healthcare.

'Government takeover'

"The American people need to understand this is about a government takeover of the whole health care system," Paul Broun, a Republican congressman, said.

In his speech at the White House, Obama said: "What's in our grasp right now is a chance to prevent a future where every day, 14,000 Americans continue to lose their health insurance, and every year, 18,000 Americans die because they don't have it."

A test vote passed the bill by 50-votes, although the actual contest is expected to be much closer.

In the test, 15 Democrats joined 177 Republicans in opposing the bill, which would cost $1.2 trillion over the next 10 years.

Even if the bill is passed it may not be voted on by the Senate until next year.

Jane Hamsher, an advocate for health care reform, told Al Jazeera: "America spends 16 per cent of its GDP on the health care ... We spend more and get less for it than any other developed nation in the world.

"People in this country are suffering now because of lack of health care ... I think 77 per cent of people want a alternative government programme ... because there's such distrust of insurance companies."