Donald Trump has suffered a major political blow as he was forced to ask Republican leaders to pull an emblematic health care bill that failed to gather enough support in Congress.

House Speaker Paul Ryan "talked to the president at three o'clock today and the president asked the speaker to pull the bill," a leadership aide in the House of Representatives said.

Mr Trump had put his reputation as a deal-maker on the line with the high-risk vote, even as Republican rebels threatened to torpedo their own party's attempt to repeal and replace Barack Obama's signature health care law.

The US leader, who made repealing Obamacare a headline campaign pledge, delivered an Oval Office statement after the stinging defeat, which called his much-vaunted deal making skills into serious question.

Mr Trump threw his full political weight into the negotiations with recalcitrant Republicans, mostly ultra-conservatives concerned the new plan was too similar to Obamacare and would cost the government too much.

On Thursday evening -- after a first delay to the vote -- Mr Trump issued a stunning ultimatum to his party demanding a vote Friday and warning that if he were to lose, Obamacare would stay in force and he would move on to other items on his agenda.

But despite the Republicans' comfortable majority in Congress and the president's vocal backing, they failed to win over the rebels, forcing them to pull the bill at the last minute to avoid a humiliating defeat.

The Republican Party's longstanding ideological divisions were laid bare in very public fashion this week, sinking President Donald Trump's Obamacare repeal plan and threatening other elements of his agenda.

The health care bill fell victim to bickering between two competing groups in Trump's party: a band of grass roots conservatives, centered around the House Freedom Caucus, who routinely buck leadership; and establishment-leaning moderates who are more likely to seek consensus over confrontation.

The president's failure to get them together and bring the American Health Care Act across the finish line highlighted how the internal fracturing has yet to heal.

That could spell trouble for the party in power, as Washington gears up for several legislative battles in the months ahead.

"Like Southern California, the GOP has many fault lines," John Pitney, a professor of American politics at Claremont McKenna College, said.

"They run in multiple directions and any one of them could cause an earthquake."

Tremors are already being felt. Congress must pass a spending bill by April 28 that funds federal operations, or government could tumble into a shutdown.

It will also begin debate in coming months on raising the US debt ceiling.

The factions are often far apart on such issues, with conservatives balking at debt ceiling hikes and moderates far more willing to consider compromise on social issues when it comes to the budget.

Disputes between the two factions is nothing new.

In 2010, ecstatic grassroots Tea Party candidates rode into Congress on a wave of anti-establishment fervor, as Republicans seized control of the House of Representatives.

The following year, bitter Republican battles over raising the debt ceiling nearly drove the United States into a calamitous default.

In October 2013, rancorous fights over spending led to a 17-day government shutdown, largely blamed on conservatives like Senator Ted Cruz.

Getting Republicans to line up on issues has often been like herding cats.

One need only look back to 2015, when the far-right managed to drive House speaker John Boehner into retirement after he tried to drag them into line on multiple fronts.

Many conservatives openly celebrated Boehner's departure -- he once called Cruz a "jackass."

But Boehner was replaced by the wonkish, rising young star Paul Ryan, a consumate establishment Republican and former vice presidential candidate.

While he faced criticism from far-right legislators, Mr Ryan managed to tamp down the uproar by conservatives -- until the 2016 presidential race and the emergence of Trump, the populist candidate.

Trump's November election victory has clearly emboldened core conservatives and far-right ideologues, leaving some middle-of-the-road Republicans in political purgatory on issues like health care and immigration.

Republicans would most likely need to be far more united than Friday's debacle if the party is to successfully tackle the coming legislative laundry list.

Immediately after Friday's health bill collapse Mr Trump declared that "now we're going to go for tax reform," an issue as complex and thorny as health care reform -- and to date more elusive.

Mo Brooks, a Freedom Caucus congressman, downplayed the divisions as he looked ahead.

"I see no impact whatsoever from the failure of this bill today with respect to what the prognosis may be for tax reform, border security or any of those other issues. They're entirely different," he said.

But sniping within the ranks was spilling into the open Friday.

"The House Freedom Caucus just single-handedly saved #Obamacare," tweeted Adam Kinzinger, a moderate House Republican, blaming intransigent conservatives for the health bill's failure.

Pitney said Mr Trump will need to navigate the political fault lines carefully if he is to rally Republican troops to his causes.

"Trump will have a very hard time dealing with these divides because he does not understand them," Pitney said.

"Trump needs to learn about Congress and public policy. I doubt that he will do so."

With AFP