Top aides to President Barack Obama confidently predicted Sunday that his signature healthcare overhaul would finally pass through Congress this week after a year of costly political wrangling.

"I think we will have the votes to pass this," said David Axelrod, Obama's senior adviser, as their Democratic Party allies in the House of Representatives prepared the final push for the reform legislation.

Obama on Friday delayed a trip to Asia by three days, until March 21, in hopes the plan that would extend health coverage to 31 million uninsured Americans could be voted into law and reach his desk for signature before he left.

Democratic leaders in the House are struggling to garner the 216 votes needed to adopt a measure already passed in the Senate, even though they hold more than 250 seats in the 435-member chamber.

"It's a struggle, but I believe we are moving in the right direction," Axelrod said on CNN television.

Obama's spokesman, Robert Gibbs, was equally confident.

"I think the House will have passed the Senate bill a week from today," he said on CBS's Face the Nation program.

"This is the week where we will have this important vote," he said.

In addition to extending health coverage to uninsured Americans, the legislation would impose restrictions on insurance companies, notably barring them from refusing coverage to people with pre-existing health conditions.

Opposition Republican lawmakers unanimously oppose Obama's plan, claiming it would push up health insurance costs for consumers, expand the government's reach unnecessarily and add to the country's skyrocketing debt.

Democrats, pointing to independent analyses which show the plan would lower health insurance premiums for most people and reduce the federal budget deficit, say the Republican opposition is simply aimed at wounding Obama politically ahead of key midterm elections in November.

But the reform plan now under consideration also faces opposition among House Democrats, some of whom say it doesn't go far enough in reining in private insurers and others who want tougher safeguards against using insurance to pay for abortions.

The White House and its allies have devised an intricate plan that would have House Democrats pass a Senate version of health reform that was less far-reaching than an earlier House bill and included some controversial spending designed to attract votes from key senators.

Obama would sign the bill into law before leaving for Asia, and then both chambers would pass "fixes" to the legislation demanded by the House Democrats.

That process, known as "reconciliation", would let Democrats frustrate Republican filibuster obstruction tactics in the Senate and allow the healthcare overhaul to be finalized before Congress goes into recess on March 26.

"This is about as complicated as it gets as a procedural matter," said professor Steven Smith, a congressional scholar at Washington University, St Louis.

Obama's presidency has been consumed by health care reform, at a time when many Americans tell pollsters they would prefer that he concentrate on creating jobs amid crippling 9.7 percent unemployment.

To fail, after investing so much political capital would be a disaster.

"I think it would be a pretty serious defeat for him and cause him fairly serious problems," said Smith.

Obama would see his credibility compromised, and struggle to frame coalitions on tough agenda issues like climate change and immigration reform.

Failure would also call into question the capacity of Democrats to govern, given their control of the House, Senate and the presidency.

And they would have to face grass roots liberals in the mid-term elections in November without a victory sought by Democrats for decades.