US President Donald Trump is heading for a too-close-to-call vote on his troubled healthcare bill in the House.
Mr Trump would suffer a huge blow if one of his major election pledges, to repeal and replace the programme known as Obamacare, fell at the first hurdle.
Asked on Friday about the vote, he just said: “We’ll see what happens.”
Even if the bill does pass the House, it could face a tougher passage in the Senate, where Republicans have only a slender majority.
A debate on the American Health Care Act is taking place in the House of Representatives, with the crucial vote scheduled for later on Friday.
Mr Trump needs a minimum of 215 Republicans to vote for the bill. If 22 join the Democrats, the bill will fail.
But US media tallies suggest between 28 and 35 Republicans still remain opposed.
House Speaker Paul Ryan visited the White House on Friday to give Mr Trump an update on the numbers, with US media reporting that there were not enough.
White House press secretary Sean Spicer said that No votes were still being won over and “we are getting closer and closer”, but suggested it was unclear whether the 215 threshold would be reached.
He said the president had “given his all” and “left everything on the field” in trying to win over votes.
Mr Spicer said the vote was still scheduled for 15:30 (19:30 GMT) and it was “now up to the members of the House to decide”.
On Thursday, Mr Trump reportedly told mutinous Republicans that if they did not vote for his bill – dubbed Trumpcare by Democrats – they would be stuck with President Obama’s act for good, and he would move on with the rest of his agenda.
Woefully unpopular – Anthony Zurcher, BBC News, Washington
The moment Republicans have been anticipating for seven years has almost arrived. They will have the chance to take a major first step toward rolling back the healthcare reform passed by Barack Obama and Democrats.
So why is it that almost no Republicans seem happy?
Moderates are upset that the proposed legislation cuts health coverage too much. Hard-liners are angry the changes don’t go far enough. Donald Trump is warning that if things don’t go his way, he’ll abandon the whole effort.
The president’s move effectively forces the hand of recalcitrant members of Congress. The moderates seem unlikely to budge, so it all comes down to the libertarian-leaning Freedom Caucus conservatives. Is half a repeal loaf better than no loaf at all?
Looming over all of this is the stark reality that the proposed legislation is woefully unpopular with the public at large – garnering just 17% approval in one recent poll. Conservative interest groups are sharply divided over whether to support the bill or not.
What should have been a moment of triumph for Republicans in Congress has turned into an exercise in political pain minimalisation.
Mr Trump has already suffered one setback when Republican leaders delayed a Thursday vote in the House, which the White House had insisted it would win.
The president kept up the pressure on Friday morning, tweeting “this is finally your chance for a great plan!”
Another tweet targeted the conservative Freedom Caucus, many of whose members have opposed the bill.
Though Mr Trump gave little away when asked about the vote on Friday, he did say Mr Ryan should stay on even if the measure collapsed.
Repealing Obamacare was a major plank of Mr Trump’s election campaign, but its replacement has stalled amid Republican infighting, with the current reforms going too far for some and not far enough for others.
A number of controversial last-minute changes were made to placate conservatives, including ending Obamacare’s requirement that insurers cover “essential benefits” including maternity care, mental health services and prescription drugs.
But it was unclear if this was enough to sway them.
In the House debate, Republican supporters of the bill targeted both what they called the failures of the Obamacare but also the need to honour the pledge the party had made in the election.
Democrats railed against the content of the bill, saying it was less about health and more a tax rebate for the wealthy. Many read out case studies of people who had benefited from Obamacare.
More on the healthcare story
- What are the Republicans proposing?
- High stakes for Trump on healthcare vote
- All-male White House health bill photo sparks anger
- Trump health bill: Winners and losers
- Is Obamacare more popular than ever?
- A bumpy 24 hours for Trump health bill
Obamacare helped 20 million previously uninsured Americans get health insurance but has been plagued by increases in insurance premiums, which were also a problem before the health law.
Mr Trump promised a new law that would cover more people and at a lower cost. The Republican bill keeps some of the popular elements of Obamacare but limits future federal funding for Medicaid, which covers low-income people.
A new estimate by the Congressional Budget Office released on Thursday evening said recent changes to the bill would make it costlier than previously thought.
The number of uninsured Americans would rise by 24 million by 2026 under the new law, the budget analysis said.
Key elements of the new bill:
- Cuts the Medicaid programme for low earners
- Provides tax credits to help people pay medical bills, but reduced compared to Obamacare
- Ends penalties on those who do not buy health coverage
- Allows insurers to raise premiums for older people
- Blocks federal payments to women’s healthcare provider Planned Parenthood for a year
US healthcare bill: Knife-edge vote looms for ‘Trumpcare’