Donald Trump warned Republicans that he is done negotiating and wants a vote Friday, March 24 on dismantling Obamacare, setting up a high-stakes showdown with members of the president's own party over his embattled health care plan, AFP reports.

House leaders were forced to postpone a Thursday vote on the measure amid a revolt by mainly conservative Republicans, who were complicating the first major legislative test for the new president by signaling it would not pass without key changes.

Trump himself set the stage, dispatching an aide to a closed-door meeting of Republican lawmakers to demand a Friday vote.

"The message is tomorrow it's up, it's down -- we expect it to be up -- but it's done tomorrow," White House budget director Mick Mulvaney told the lawmakers, according to congressman Chris Collins.

Mulvaney then delivered Trump's extraordinary ultimatum.

"If it doesn't pass, we're moving beyond health care," Mulvaney said, paraphrased by Collins.

"We would be moving on to other parts of his agenda."

The idea that Trump -- who campaigned relentlessly on a pledge to bury Barack Obama's signature legislative accomplishment -- would wash his hands of the fight and let Obamacare stand is a startling departure from the party playbook.

But Mulvaney's blunt take-it-or-leave-it approach could be part of Trump's hardball strategy to get Republican rebels to fall in line.

House Speaker Paul Ryan, a champion of the legislation dubbed the American Health Care Act, put on a brave face despite the bill's hanging by a thread.

"We have been promising the American people we will repeal and replace this broken law because it's collapsing and failing families, and tomorrow we're proceeding," he told reporters after the conference meeting.

A procedural vote on the bill is set for approximately 10:00 am (1400 GMT) Friday, followed by a full floor vote in the afternoon.

The president and his lieutenants had repeatedly voiced optimism about the bill's prospects, saying they had made progress convincing doubters to join Trump's camp.

But the votes weren't there.