Facing growing opposition from members of his own party, Senate Majority Leader Mitch McConnell has delayed the vote on the Republicans' healthcare bill until after Congress's 4 July recess.

The schedule change is another setback for Donald Trump's effort to repeal and replace Obamacare – officially known as the Affordable Care Act – which he has repeatedly referred to as "dead".

Mr Trump told reporters on Wednesday that "healthcare is working along very well...we're gonna have a big surprise. We have a great healthcare package."

When asked what that meant, Mr Trump responded "we're going to have a great, great surprise."

Senate Majority Leader Mitch McConnell is reportedly trying to revise the healthcare bill by Friday.

Mr Trump summoned all 52 Republican senators to the White House on Tuesday afternoon to discuss how to proceed after the vote postponement – with Democrats appearing to recognise the potential to turn their staunch opposition to the bill into a complete defeat for the Trump administration.

"I think the Senate bill is going to be great," Mr Trump said to reporters at the start of the meeting with Republicans.

During his opening remarks, the President declared that Obamacare "is melting down", adding that Senate Republicans and the White House are "getting very close" to reaching agreement on a path toward getting the votes needed to pass the latest healthcare bill.

"This will be great if we get it done," Mr Trump said. But appearing to recognise the opposition the bill faces, he added: "And if we don't get it done, it's just going to be something that we're not going to like. And that's okay, and I understand that very well."

"But I think we have a chance to do something very, very important for the public – very, very important for the people of our country that we love."

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Republican legislators' overlapping concerns and competing interests have presented Mr McConnell with a balancing act. Moderate senators worry that millions of people would lose their insurance, while conservatives assert that the bill does not do enough to erase Democratic former President Barack Obama's signature domestic legislation.

Speaking after the meeting with Mr Trump, Mr McConnell said that Republicans need to find a solution as negotiating with Democrats will not bring the changes that those Republicans with concerns would want. He added that the party stands a good chance of getting a bill on the Senate floor but "just not this week".

“I think the meeting was very helpful,” Mr McConnell said. “I think everyone around the table is interested in getting to yes ... Because we know the status quo is simply unacceptable, unsustainable and no action is just not an option.”

When Mr McConnell postponed the vote early in the afternoon, at least five senators had suggested they would vote against the motion to begin debate on the bill, which was originally scheduled to hit the Senate floor on Wednesday.

The defectors included centrist Susan Collins of Maine, moderate Dean Heller of Nevada, and conservatives Rand Paul of Kentucky, Mike Lee of Utah and Ron Johnson of Wisconsin.

The Senate plan significantly scales back Medicaid – a healthcare programme for the poor – repeals Obamacare’s taxes on the wealthy, and defunds Planned Parenthood for a year.

After the delay in the vote, more Republican Senators spoke out about their concerns. Senators Rob Portman of Ohio, and Shelley Moore Capito of West Virginia issued a joint statement saying they had concerns about the changes to Medicaid, while Ms Capito raised the ill-effect the changes could have on efforts to fight drug addiction.

Another Republican Senator, Jerry Moran of Kanas said the plan "missed the mark" for his state and he was "pleased" to get the chance to try and ensure changes to the bill.

The leading Democrat in the Senate, Chuck Schumer, said that the lack of consensus over the healthcare bill has proved that it is fundamentally flawed "at the centre", but that his party knows "the fight is not over" regarding Republican plans to push the bill through.

"Over the next couple of weeks, we know that Leader McConnell will try to use a slush fund to buy off Republicans, cut backroom deals to try and get this thing done. So we’re going to watch this bill," Mr Shumer said at a press conference following the announcement of the vote's postponement.

Trump says 'Obamacare is dead' as he prepares to repeal and replace healthcare act

He added that he is willing to work with Republicans, but suggested that his colleagues across the aisle "first, abandon tax breaks for the wealthy, abandon cuts to Medicaid, abandon repeal".

"And we can sit down and talk about improving healthcare," Mr Schumer said.

Mr Schumer said earlier that the Democrats have a good chance of defeating the bill whether that is "a week from now, a month from now [or] a year from now".

As for Mr McConnell, he had said earlier in the day that healthcare is "a big complicated subject" and complicated bills are "hard to pull together and hard to pass".

With a majority of 52 Republicans to 48 Democrats in the Senate, Mr McConnell can only afford to lose two votes on both the motion to begin formally considering the bill – known as the motion to proceed – as well as on the bill itself. In the event of a 50-50 tie, Vice President Mike Pence will cast the deciding vote.

Mr McConnell and the Senate Republican leadership, who unveiled their healthcare measure last Thursday, had been pushing for a vote on the bill by the end of the week and the start of the recess.

The bill's prospects were not helped by an analysis by the nonpartisan Congressional Budget Office saying the measure would cause 22 million Americans to lose medical insurance over the next decade. The report prompted Senator Collins, a key moderate vote, to say she could not support moving forward on the bill as it stands.

Ms Collins told reporters that if the bill stalls on the motion to proceed to debate, she hopes "it would mean that we will go back to the drawing board, work in a bipartisan fashion to correct the very real problems that do exist with the Affordable Care Act".

Ms Collins, along with Republican Senator Lisa Murkowski of Alaska, also oppose the bill's defunding of Planned Parenthood.

"Senator Murkowski and I are going to team up to offer an amendment having to do with the elimination of federal funding for Planned Parenthood," Ms Collins said. "We both believe that it makes no sense to exclude Planned Parenthood from the Medicaid programme."

In a statement, Planned Parenthood president Cecile Richards called the Republican plan “the worst bill for women’s health in a generation”.

With the threat of a vote after the recess week, Mr Richards warned that it was “now more important than ever for people to make their voices heard”.

“Republican leadership needs to hear over and over that the people of America will not stand to see healthcare stripped from millions, and they will not stand to see Planned Parenthood’s patients lose their access to healthcare,” she said.

Passing the healthcare measure would hand Mr Trump a legislative win as he seeks to emerge from weeks of questions over Russia's role in last year's US presidential election.

During a White House press briefing, Deputy Press Secretary Sarah Huckabee Sanders said the President is still "hoping to create consensus that will push this bill over the finish line", adding that he has met with several Republicans who have said they can't support the healthcare measure in its current form, including Rand Paul, Ted Cruz, Shelley Moore Capito and Ron Johnson. Senators Rob Portman and Jerry Moran have also said they can't support the present version of the bill.