President Donald Trump could be on course to make good on one of his key election pledges when the US House of Representatives votes later on dismantling Barack Obama's signature health reform.
After Mr Trump failed to convince enough of his own party representatives to back him in March, the party now believes it will finally have the votes to repeal and replace the Affordable Care Act, known as Obamacare.
Around 20 million previously uninsured Americans have gained health coverage under Obamacare.
The Republican party, which controls both the House and Senate, has said the scrapping of the health law is a top priority.
However, even if the bill clears the House by a narrow majority, it still faces a steep climb in the Senate, where only a few defections could kill the effort.
Mr Trump has called the scheme a "catastrophe" which had to be overhauled "very, very quickly".
But his first attempt to repeal it - in the first big test of his presidency - failed.
He and his supporters have spent days frantically trying to gather support from politicians who complain either that the reforms go too far or not far enough.
Mr Trump has struggled to balance the demands of the ultra-conservative Freedom Caucus, who want to scrap more of the Affordable Care Act's benefits and insurance requirements, and moderates in the Tuesday Group, who fear the bill will leave millions of Americans worse off.
The legislation's prospects brightened after members of the Freedom Caucus, who played a key role in derailing the original version of the repeal bill last month, said they could go along with a compromise.
Asked whether they had the votes needed to pass the bill, House Majority Leader Kevin McCarthy said: "We have enough votes,"
"It'll pass. It's a good bill," he added.
Called the American Health Care Act, the Republican bill would repeal most Obamacare taxes, including a penalty for not buying health insurance.
It would also cut funding for Medicaid, which provides insurance for the poor.
Medical groups, including the American Medical Association, are opposed to the revised bill and argue millions of Americans will lose coverage or face higher costs.