Washington, March 21 (DPA) Democrats in the US House of Representatives were preparing for a showdown over a critical vote Sunday on a sweeping overhaul of the health care system.

President Barack Obama was on Capitol Hill Saturday rallying Democratic lawmakers, who believed they had secured enough support - the 216 votes needed for the health legislation to pass.

'Clearly, we believe we have the votes,' said Steny Hoyer, the second-highest ranking House Democrat. 'We expect we have the votes to pass the Senate bill'.

But a group of about 10 Democrats was still not on board, over concerns that the bill would permit federal funding of abortions.

The House is expected to vote Sunday on a package of reforms aimed at imposing new controls on the practices of insurance companies and extending coverage to more than 30 million Americans who lack health insurance.

'Let's get this thing done,' Obama said, urging lawmakers to back the measure in the House.

There have been countless 'pivotal' moments in the long-running debate on reforming US health care. Sunday's vote is perhaps the biggest yet.

Obama and his fellow leaders in the Democratic Party have been engaged in a last-minute scramble to win support for their top domestic priority, which has sharply divided the country during more than a year of bitter debate.

'This piece of historic legislation is built on the private insurance system that we have now and runs straight down the centre of American political thought,' Obama told House Democrats.

'We are making sure that the system of private insurance works for ordinary families,' he said, calling the legislation a 'patient's bill of rights on steroids' and 'the toughest insurance reform in history'.

Urging lawmakers to pass the bill, Obama said: 'If you agree that the system is not working for ordinary families, if you've heard the same stories that I've heard everywhere, all across the country, then help us fix the system'.

Republicans are united in opposition, the public is divided, and many moderate Democrats are still wavering over whether to support the controversial health reforms.

The House 'should not vote blindly on an issue that is so important to every American. We deserve to have all the facts about how much this bill raises health care costs before we vote,' said John Boehner, the top Republican in the House.

Boehner is hoping public anger will translate into electoral gains in November, when one-third of the Senate and the entire House will be up for grabs in mid-term congressional elections. Democrats fear the failure to pass the reforms would be even more damaging, and are gambling the storm will pass once health care is actually approved.

'This is not over,' Boehner said. 'They do not have the votes yet. We've got to keep working to make sure that they never, ever, ever, ever get the votes to pass this bill.'

The House will vote on a version of the legislation that was approved by the Senate in December, but will also adopt a round of changes that will have to go back to the Senate for final approval.

The Congressional Budget Office (CBO), a non-partisan arbiter of legislative costs, last week estimated that the reforms will cost $940 billion over 10 years and expand coverage to about 32 million more Americans.