U.S. Senate leaders scrambled Tuesday to rescue their health-care bill, in deepening jeopardy as opposition from rebellious Republicans intensified.

Lacking the necessary votes to pass the bill, Republican leaders in the Senate decided to delay a planned vote this week until after the July 4 recess.

"This will be great if we get it done 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 OK and I understand that very well," Trump said before meeting with Republican senators at the White House.

Afterwards, Senate Majority Leader Mitch McConnell said "the meeting was very helpful." He struck an optimistic note on the bill's prospects. "We've got a really good chance of getting there, it will just take a little bit longer."

Shortly before the meeting, three more Republican senators — Jerry Moran from Kansas, Rob Portman from Ohio and Shelley Moore Capito from West Virginia — announced their opposition to the draft Better Care Reconciliation Act.

The defections proliferated after Congress's nonpartisan budget referee said the measure would leave 22 million more people uninsured by 2026 than former president Barack Obama's law.

McConnell was hoping to staunch his party's rebellion, a day after the Congressional Budget Office released its report.

The CBO analysis suggested some ammunition Republican leaders could use, saying the Senate bill would cut federal deficits by $202 billion US more over the coming decade than the version the House approved in May. Senate leaders could use some of those additional savings to attract moderate votes by making Medicaid and other provisions more generous, though conservatives would rather use that money to reduce red ink.

Moderates, conservatives against plan

The projected boost in uninsured people fed concerns by moderate Republican lawmakers that the Senate measure, annulling parts of Obama's 2010 overhaul, was too drastic. Yet conservatives were unhappy that it didn't do enough to dismantle Obama's law and lower premiums by repealing coverage requirements, leaving McConnell with little margin for error — the bill fails if three of the 52 Republican senators join the Democrats and independents to vote no.

The 22 million extra Americans were just one million fewer than the number the budget office estimated would become uninsured under the House version. Trump has called the House bill "mean" and prodded senators to produce a package with more "heart."

Minutes after the CBO report's release, three senators threatened to oppose a procedural vote to begin debate on Wednesday — enough to derail the legislation.

Early Tuesday, five Republican senators said they were opposed to starting a debate on the bill.

Also on Tuesday, Utah Senator Mike Lee said he didn't want to see debate started. He''s among the conservative senators that favour a fuller repeal of Obamacare.

Moderate Senator Susan Collins said she would vote no. Ahead of the meeting with Trump, she said, "it's hard for me to see how the president and his team are going to come up with a bill that can gather enough Republican support, given the objections from Senators who are more conservative and those of us who are more moderate."

Conservative Senator Rand Paul said he would oppose that motion unless the bill was changed. And fellow conservative Ron Johnson said he had "a hard time believing" he'd have enough information to back that motion this week.

Paul tweeted Tuesday he was meeting with the president about the bill.

I'll discuss w/ him how to fix bill & get more to a YES on real repeal, things I've tried to tell Senate leaders with no result so far —@RandPaul

Moderate Senator Dean Heller on Friday said he'd oppose the procedural motion without alterations.

Concerns over coverage reduction

Those rebels were just part of McConnell's problem. Two other conservatives — Ted Cruz from Texas and Lee — have also said they'd vote no without revisions, and several other moderates have expressed worries about the bill's Medicaid cuts and reductions in people with coverage.

Mike Lee became the fifth Republican senator to oppose letting the Senate formally begin considering the health-care bill. The conservative senator favours a fuller repeal of Obamacare. (Rick Bowmer/Associated Press)

The budget office report said the Senate bill's coverage losses would especially affect people between ages 50 and 64, before they qualify for Medicare, and with incomes below 200 per cent of poverty level, or around $30,300 for an individual.

In one example, the report says that in 2026 under Obama's law, a 64-year-old earning $26,500 would pay premiums amounting to $1,700 a year, after subsidies. Under the Senate bill, that person would pay $6,500, partly because insurers would be able to charge older adults more.

The Senate plan would end the tax penalty that law imposes on people who don't buy insurance, in effect erasing Obama's so-called individual mandate, and on larger businesses that don't offer coverage to workers.

It would let states ease Obama's requirements that insurers cover certain specified services like substance abuse treatments, and eliminate $700 billion worth of taxes over a decade, CBO said, largely on wealthier people and medical companies that Obama's law used to expand coverage.

Cuts to Medicaid

It would cut Medicaid, which provides health insurance to over 70 million poor and disabled people, by $772 billion through 2026 by capping its overall spending and phasing out Obama's expansion of the program. Of the 22 million people losing health coverage, 15 million would be Medicaid recipients.

CBO said that under the bill, most insurance markets around the country would be stable before 2020. It said that similar to the House bill, average premiums around the country would be higher over the next two years — including about 20 per cent higher in 2018 than under Obama's statute — but lower beginning in 2020.

But the office said that overall, the Senate legislation would increase out of pocket costs for deductibles and copayments. That's because standard policies would be skimpier than currently offered under Obama's law, covering a smaller share of expected medical costs.

In another troublesome finding for the legislation, the budget office warned that in some rural areas, either no insurer would be willing to participate in the individual market or the policies offered would be prohibitively expensive. Rural America was a stronghold for Trump in the 2016 presidential election.

Tax cuts for millionaires

Under the Senate bill, millionaires would get tax cuts averaging $52,000 a year, while middle-income families would get about $260 in tax cuts, according to a new analysis of the foundering bill.

The analysis was done by the nonpartisan Tax Policy Center. It found that half of the tax cuts would go to families making more than $500,000 a year.

"Much like the House-passed American Health Care Act, the Senate leadership's health bill includes a huge tax cut that mostly benefits the nation's highest-income households," Howard Gleckman, a senior fellow at the Tax Policy Center wrote on the group's website.

For example, families making $20,000 a year would get an average tax cut of about $200. But the super rich, those making $5 million or more, would receive an average tax cut of nearly $250,000.

The bill would repeal a tax on wealthy investors, saving them about $172 billion over the next decade.