WASHINGTON — House GOP leaders postponed a much-anticipated vote Thursday on legislation to overhaul the Affordable Care Act amid a Republican revolt that raised doubts about the fate of the measure as well as President Donald Trump's self-proclaimed negotiating skills.

After initially vowing to continue talks through the night, a frustrated White House told a group of GOP lawmakers meeting in the Capitol basement Thursday evening that negotiations were over and a vote would take place Friday. 

If the bill is defeated, Trump threatened to simply leave the current health care law in place and move on to other issues, according to a “take it or leave it” message delivered by Trump's budget chief Mick Mulvaney, according to Rep. Chris Collins, R-N.Y.

It remained unclear whether Trump's extraordinary ultimatum was real or a pressure tactic designed to bring unruly Republicans in line.

Despite personal appeals from the president and a flurry of last-minute negotiations with House Speaker Paul Ryan, R-Wis., wary GOP lawmakers remained unconvinced, leaving leaders shy of the votes needed to advance the controversial legislation.

Conservatives argued the bill did not go far enough in dismantling the health care law known as Obamacare and were pushing to remove a key provision of the current law that requires health plans to cover a basic set of benefits.

Centrist Republicans, including many from districts that Trump lost, were worried about projections that 24 million more people would be without coverage under the GOP bill than under Obamacare.

But options for generating more support appeared limited because making concessions to one faction risked losing support from the other.

For lawmakers, the delay meant more time to be hammered by advocacy groups from all sides. Leading patient advocates, physician groups and hospitals have bombarded them with dire warnings about the erosion in coverage. Businesses groups have lined up on both sides of the bill; conservative organizations backed by the Koch brothers, which oppose the bill as too weak, pledged ad campaigns to encourage votes against the measure

The Thursday vote had been purposefully scheduled for the law's seven year anniversary.

At the White House, Trump had hoped that a decisive victory in the effort to repeal Obamacare would provide political momentum to propel other ambitious efforts, such as overhauling the nation's tax code, pursuing new trade deals and dramatically scaling back federal spending.

The president made a hard sell in recent days, warning Republicans they risked losing their congressional majority in the next election if they failed to support the bill.

But Trump's struggle to deliver, which seemed complicated at times by his lack of understanding of the complexities of the health care legislation, threatened to tarnish his image as a deal-maker.

“Rookie's error, Donald Trump,” said House Minority Leader Nancy Pelosi, D-Calif., who ushered passage of the Affordable Care Act under Obama. She mocked Trump for scheduling a vote before the votes were lined up.

The conservative House Freedom Caucus led the opposition, re-establishing itself as one of the party's most formidable power centers.

Backed by Senate allies, including Sen. Ted Cruz, R-Texas, and Sen. Rand Paul, R-Ky., the caucus at times bypassed Ryan and negotiated directly with the White House.

The vote delay raised familiar questions about who is in control of the GOP and dealt an embarrassing setback to Ryan. Facing solid opposition from Democrats, the speaker must rely on the GOP for passage and can lose no more than about 21 Republicans. Defections at one point this week spilled beyond 30.

Republican leaders worked late into the night to cut a deal with the caucus. Conservatives wanted a full repeal of the Affordable Care Act's mandates, including 10 essential health benefits, such as maternity coverage, that insurers are required to provide.

While the White House appeared willing to compromise, the caucus splintered Thursday, and Trump was unable to close the deal.

Some members of the group complained the compromise did not go far enough to meet their concerns. “They haven't met us at all,” said Rep. Paul Gosar, R-Ariz.

Rep. Mark Meadows, R-N.C., the caucus chairman, was hopeful a deal would be reached. “No deal yet, but negotiations haven't stopped.

A new analysis released Thursday from the nonpartisan Congressional Budget Office showed changes so far would still leave 24 million more Americans without insurance, but would only reduce the deficit by half as much as initially proposed.

Washington Bureau's Brian Bennett contributed.

lisa.mascaro@latimes.com