The House vote on the American Health Care Act had been scheduled for late Thursday, but it was postponed after administration officials failed to convince skeptical conservative Republicans to support the bill. The delay was an embarrassing setback for Trump and his GOP allies.
The White House and Republican leaders such as House Speaker Paul Ryan had hoped for a roll call on Thursday, which marked the seventh anniversary of Obama's enactment of his landmark health care statute that Republicans have vowed ever since to get rid of.
After the delay, Trump claimed he was finished negotiating with GOP holdouts and determined to pursue the rest of his agenda, win or lose.
It's expected a vote will be held on Friday, despite deep uncertainty over whether the Republican party has enough votes to prevail over the Democrats and other opponents of the plan.
"We have been promising the American people that we will repeal and replace this broken law because it's collapsing and it's failing families. And tomorrow we're proceeding," Ryan tersely told reporters after scheduling what loomed as the most momentous vote to date for Trump and for the Wisconsin Republican's own speakership.
The vote stood as an early crossroads in Trump's young presidency. Victory would clear an initial but crucial hurdle toward achieving the GOP's lodestar quest to repeal former President Obama's 2010 health care overhaul. Defeat could weaken his political potency by adding a legislative failure to a resume already saddled with inquiries into his campaign's Russia connections and his unfounded wiretapping allegations against Obama.
There was no evidence that leaders' decision to charge ahead was a feint and that they'd delay again if necessary. Instead, they seemed to be calculating that at crunch time, enough dissidents would decide against sabotaging the bill, Trump's presidency, and the House GOP leadership's ability to set the agenda.
Even if they prevail, Republicans still will face an uphill climb in the Senate, where conservatives and moderates are also threatening to sink the plan.
The GOP bill eliminates the Obama statute's unpopular fines on those who do not obtain coverage and the often generous subsidies for those who purchase insurance.
Instead, consumers would face a 30% premium penalty if they let coverage lapse. Republican tax credits would be based on age, not income. The bill would also end Obama's Medicaid expansion and trim future federal financing for the federal-state program. It would also let states impose work requirements on some of its 70 million beneficiaries.
In a bid to coax support from conservatives, House leaders proposed a fresh amendment — to be voted on Friday — repealing Obama's requirement that insurers cover 10 specified services like maternity and mental health care.
Conservatives have demanded the removal of those and other conditions the law imposes on insurers, arguing they drive premiums skyward.
Many moderates are opposed because they say the GOP bill would leave many voters uninsured. Medical associations, consumer groups, and hospitals are opposed or voicing misgivings. Some Republican governors say the bill cuts Medicaid too deeply and would leave many low-income people uncovered.
Republicans can lose only 22 votes in the face of united Democratic opposition. A tally by The Associated Press found at least 32 "no" votes, but the figure was subject to fluctuation amid frantic GOP lobbying.
Rep. Mark Meadows, head of the hard-right House Freedom Caucus, said he remained a "no" but didn't answer when asked whether the group still had enough votes to kill the legislation. He'd long said their opposition alone would defeat it without changes.
Trump went after the caucus earlier on Friday, saying that a vote against the health care bill would favour Planned Parenthood.
The president tweeted, "the irony is that the Freedom Caucus, which is very pro-life and against Planned Parenthood, allows P.P. to continue if they stop this plan!"
However, other foes said they'd not flipped. These included moderate Reps. Charlie Dent of Pennsylvania, Dan Donovan of New York and Leonard Lance of New Jersey, plus conservative Walter Jones of North Carolina, who had his own words of warning.
"He's there for three-and-a-half more years," Jones said of Trump. "He better be careful. He's got a lot of issues coming."
The nonpartisan Congressional Budget Office said changes Republican leaders had proposed before Thursday to win votes had cut the legislation's deficit reduction by more than half, to $150 billion over the next decade. But it would still result in 24 million more uninsured people in a decade.
Obama's law increased coverage through subsidised private insurance for people who don't have access to workplace plans, and a state option to expand Medicaid for low-income residents. More than 20 million people gained coverage since the law was passed in 2010.