Image caption The healthcare reform has divided US public opinion

Republican leaders have begun a bid to overturn the healthcare law signed by US President Barack Obama in 2010.

A bill to repeal the landmark law was formally unveiled on Monday evening, two days before Republicans assume control of the lower house of Congress.

It is set to be voted on by the House of Representatives on 12 January.

But the vote is expected to be largely symbolic as Democrats retain a Senate majority and can block the move and the president could ultimately veto it.

'Jewel in crown'

The Republicans won sweeping gains in November's mid-term congressional elections in part by attacking what they portrayed as a costly and job-killing healthcare law.

The BBC's Steve Kingstone, in Washington, says healthcare reform is so far the legislative jewel in the crown of President Obama's administration.

What remains to be seen is whether this is simply a symbolic flexing of muscles by the Republicans, or whether it sets the tone for two years of party-political acrimony, our correspondent says.

With power in Congress divided, Democrats and Republicans must work together if new laws are to be passed.

On Tuesday Mr Obama appealed to Republican congressional leaders to put partisan politics aside to rebuild the US economy.

Speaking on board Air Force One as he travelled back to Washington from a holiday in Hawaii, Mr Obama said: "You know, I think that there's going to be politics. That's what happens in Washington - that they [Republicans] are going to play to their base for a certain period of time.

"But I'm pretty confident that they're going to recognise that our job is to govern and make sure that we are delivering jobs for the American people and that we're creating a competitive economy for the 21st Century, not just for this generation but for the next one."

The US healthcare reform law was approved in March last year, making it compulsory for Americans to buy medical insurance and illegal for insurance companies to deny coverage to customers with pre-existing conditions.

If, as expected, the attempted repeal fails, the Republicans will attack the law through other means, specifically by using congressional committees to cut off relevant funds, our correspondent says.