President Donald Trump faced a titanic showdown in Congress later today with a crucial vote to repeal and replace Obamacare hanging in the balance and too close to call.

In a high stakes gamble Mr Trump issued a take-it-or-leave-it ultimatum to rebel Republicans, indicating that if the measure fails he will leave Obamacare in place and move on to other priorities.

Mr Trump was said to be "agitated" by the reluctance of conservative Republican congressmen to vote for the American Health Care Act because they do not believe it goes far enough in dismantling Obamacare.

Republicans have a majority in the House of Representatives but they can only afford to lose 21 votes from their own side. Democrats will all vote against the bill..

However, with only hours to go before an expected vote at least 35 Republicans still planned to vote against, despite last minute concessions from Mr Trump and his allies.

Defeat would be a huge setback to Mr Trump instilling doubts about his ability to carry his own party with him in Congress not only on healthcare but other major platforms of his campaign like tax reform and infrastructure investment. Global financial markets were monitoring the vote closely.