US President Barack Obama has rallied the support of Democratic lawmakers on Capitol Hill ahead of a crucial vote on sweeping healthcare reform.
Urging them to back the measure in a House vote expected in the coming hours, he said: "Let's get this done."
Democratic leaders have spent days working to get the 216 votes needed to pass the highly-contested bill.
Democratic House Majority Leader Steny Hoyer said he believed the party now had the necessary support.
Senior House Democrats have decided on a direct vote to pass a Senate version of the reform bill, rather than using a procedural measure that would have "deemed" it passed without a vote.
 |  Is this the single most important step that we have taken on health care since Medicare? Absolutely 
US President Barack Obama
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And Democratic Senate Majority Leader Harry Reid assured House lawmakers he had the "commitment of a significant majority" in the Senate to pass the next stage of the legislation, amending that bill with changes the House wants.
However, Democratic leaders can't be certain of victory, says the BBC's Mark Mardell in Washington.
If passed, the reforms will deliver on Mr Obama's top domestic priority by providing insurance to some 32 million of the Americans who currently lack coverage.
The Republicans are unanimously opposed to the legislation, which they say is unaffordable and represents a government takeover of a large part of the country's economy.
In the party's weekly radio address, House Republican leader John Boehner criticised what he said were tax increases and cuts in some benefits to pay for the bill, saying: "This is not reform."
Protesters opposed to the Democrats' proposals demonstrated outside the Capitol building in Washington, waving placards and chanting "kill the bill".
'Tough vote'
Speaking to Democrats in Washington, Mr Obama said the vote would be the single most important step taken on healthcare since Medicare, which helps the elderly, was passed four decades ago.
| Obama is trying to work the old magic, the ability to connect, that made him think he could be president in the first place
Mark Mardell
BBC North America editor |
He told lawmakers: "I know it's a tough vote."
But he said he was confident that doing the right thing for the American people would end up "being the smart thing to do politically".
"Don't do it for me, don't do it for the Democratic Party, do it for the American people. They're the ones looking for action right now," he said.
The president has held dozens of meetings and phone calls in recent days with Democratic House members wavering over whether to back the bill or not.
It remains unclear exactly how many votes the party can count on.
Some lawmakers have called for tighter language in the bill to make sure no federal money can be used for abortions, while others are concerned about cost or say its reforms do not go far enough.
If the House passes this the president will sign it in to law, although it would still go to the Senate for more changes.
Deficit reduction
The House of Representatives and the Senate adopted different versions of the bill in November and December.
Opponents of the reform bill say it represents a government takeover
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The usual procedure would be for two versions of legislation to be combined into a single bill for President Obama to sign into law.
But after Senate Democrats lost the 60-seat majority required to defeat a filibuster by Republicans, Democratic leaders decided to use a controversial procedure to ensure the bill's passage.
Under the plan, the House will vote on a package of reconciliation "fixes" amending the Senate bill.
The Senate will then be able to make changes in a separate bill using a procedure known as reconciliation, which allows budget provisions to be approved with 51 votes - rather than the 60 needed to overcome blocking tactics.
According to Congressional Budget Office, the final version of the Democrats' healthcare plan will cut the federal deficit by $138bn over 10 years.
The non-partisan body said the proposed legislation would cost about $940bn over a decade.
The reforms would increase insurance coverage through tax credits for the middle class and expansion of the Medicaid programme for the poor.
If approved, they would represent the biggest change in the US healthcare system since the creation in the 1960s of Medicare, the government-run scheme for Americans aged 65 or over.
US HEALTHCARE AND WORLD COMPARISONS
- Healthcare reform is a priority for Barack Obama. The US spends about $2.2tn a year on its system - which includes private, federal or employer schemes.