US President Donald Trump and other Republicans elected in November rode into Washington promising to undo president Barack Obama's signature health care legislation.

Yesterday, that plan failed in spectacular fashion.

Like the businessman he is at heart, Trump put all his chips on the table in his biggest political gamble since taking office in January.

Trump ignored the warning signs that a health care reform bill hammered out by House Republicans and talked up for weeks was doomed to fail.

In the brash style the New Yorker is known for, Trump told fellow Republicans, who hold a significant majority in the House of Representatives, to put the bill up for a vote - or the promise to repeal it that many of them were elected on would be over.

By the end of the day yesterday, it was, leaving a bitter taste in the mouths of Republican lawmakers who had been sold on the negotiating skill Trump frequently boasted he had.

No one openly asked whether this is how 'The Art of the Deal' (the title of Trump's bestselling 1987 book) is really supposed to work, but it's plausible that some were thinking it.

After Trump "left everything on the field," as his spokesperson put it, Republicans called his bluff and the president had to fold his hand and watch the first major legislative test of his young presidency go down in flames.

Obamacare - the nickname for the law passed by Trump's predecessor and which the current president campaigned hard and long to change - will "remain the law of the land for the foreseeable future," Speaker of the House Paul Ryan said with chagrin after pulling the bill rather than facing a vote tally that the nays would have won.

It collapsed over the same problem that has bedevilled the lower chamber in particular for years: fractures within the Republican Party.

A group of as many as 30 conservatives and libertarians in a faction called the Freedom Caucus had criticized the legislation, formally named the American Health Care Act.

For most of the Freedom Caucus, it was too grand of a plan. One called it "the largest Republican welfare programme in history".

But there also were moderates who bucked the leadership, concerned that it could result in millions of people losing their coverage.

Even if the bill fell only a few votes short, as both Trump and Ryan were keen to point out, it was still a major defeat for Trump.

It meant he failed to fulfill one of the key promises he made to voters: That he would repeal and replace former president Barack Obama's signature health care reform, signed into law seven years ago.

"We all learned a lot," Trump told reporters at the White House. "We learned a lot about the vote-getting process," said the businessman who took pride during last year's campaign in not being a politician.

He cited some "very arcane rules" in Congress, but took no personal responsibility for the loss. Instead he flipped it around, saying opposition Democrats were the losers "because now they own Obamacare".

And when it "explodes," Trump predicted, Democrats will come running into his arms, and he will be ready.

The president also said he would be open to bipartisanship in writing the next health care reform.

When Democrats "become civil" and work with Republicans, it could lead to an even better health care plan, Trump asserted.

His statements contrasted with those of a more humble Ryan, who told reporters he would not "sugar-coat" the experience.

"This is a disappointing day for us," said Ryan, whose name is closely associated with the Republican effort at health care reform.

He explained it as a growing pain for a party as it moves from opposition to governing, but also said he and his fellow Republicans would have to take time to reflect how they got to this moment.

Many certainly were not looking forward to facing voters who cast their votes for them believing they would soon feel relief from the higher costs for health insurance that have accompanied Obamacare.

Republicans will have to explain that the saga over health care in America goes on, and a debate that started decades ago with an estimated 40 million uninsured people in the country still has no resolution to satisfy the majority.

- dpa