Senate Majority Leader Mitch McConnell has said there will be no vote on a bill to repeal Obamacare this week – meaning Republicans have again failed to follow through on one of President Donald Trump's major campaign promises.

Emerging from a closed-door meeting, senators were quick to confirm that no vote would take place on the Graham-Cassidy bill. Senator Jeff Flake of Arizona shook his head and said "no" when asked about plans for a vote.

The announcement marks the end of the latest drive to overhaul the Affordable Care Act (ACA), otherwise known as Obamacare, which Republicans have been promising to repeal since former President Barack Obama signed it into law in 2010.

The party had already suffered a devastating defeat on healthcare reform this year when another Obamacare repeal bill failed on the Senate floor in July.

On Monday, Senator Susan Collins joined her Republican colleagues Rand Paul and John McCain in their opposition to Graham-Cassidy, all but ensuring the measure would not pass. Mr McConnell could only afford to lose two votes from his party, which holds a 52-seat majority in the 100-member Senate. No Democrats were expected to vote for the legislation.

From the White House, Mr Trump said he was "disappointed in certain so-called Republicans" who opposed the measure, adding, "We don't know why they did it."

Mr McCain said he disagreed with the partisan process being used to push the bill through Congress; Ms Collins had deep concerns about the legislation's cuts to Medicaid – a healthcare programme for the poor – and other effects on healthcare; and Mr Paul said Graham-Cassidy did not do enough to undo the ACA.

Mr Trump said that "at some point" there will be a repeal and replace of Obamacare.

The latest iteration of Obamacare repeal legislation, drafted by Senators Bill Cassidy and Lindsey Graham, was designed to give states funding to run their own healthcare programmes. Despite last minute changes to the legislation, 34 states and Washington, DC were expected to lose money under Graham-Cassidy, according to an analysis from consulting firm Avalere Health.

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Speaking at a news conference on Capitol Hill, Republicans downplayed the defeat by saying they were postponing the vote and would return to healthcare after focusing on tax reform.

"There are 50 votes for the substance," Mr Graham said, referring to his healthcare bill. "There are not 50 votes for the process."

Mr McConnell said that Republicans have not given up trying to change America's healthcare system.

"We are not going to be able to do that this week, but it still lies ahead of us, and we haven’t given up on that," Mr McConnell said.

After this week, procedural rules in the Senate will make it much more difficult for Mr McConnell to pass any type of healthcare reform this year without at least some Democratic support.

Republicans assert that Obamacare has destabilised individual markets for health insurance and has forced consumers to buy insurance they do not want or cannot afford.

In a separate news conference, Democrats responded to the defeat of Graham-Cassidy by calling for Republicans to resume bipartisan negotiations to stabilise the health insurance markets. Those bipartisan talks came to a standstill earlier this month after the latest Obamacare repeal plain gained momentum.