The Senate Republican health-care bill would leave 22 million more Americans uninsured in 2026 than under President Barack Obama's health-care law, the Congressional Budget Office estimated Monday, in a blow to Republican leaders' hopes of pushing the plan through the chamber this week.

The CBO coverage estimates pose yet another problem for Senate majority leader Mitch McConnell, who unveiled the legislation last Thursday. By Friday afternoon, he was facing public statements of opposition from five Republican senators — three more defections than he can afford and still win approval for the legislation over united Democratic opposition. Others have expressed concerns.

The White House responded by attacking the CBO, saying it has a "history of inaccuracy."

The White House says the CBO "has consistently proven it cannot accurately predict how health-care legislation will impact insurance coverage."

Threats of opposition from three Republican senators are casting doubt on whether Republican leaders have enough support to move ahead on the Senate health-care bill.

The Senate has to hold a procedural vote to move forward, most likely on Wednesday.

Senator Susan Collins of Maine tweeted after the Congressional Budget Office analysis on Monday that the Senate bill won't fix the flaws in the current bill. She says she will vote no on the "motion to proceed."

Senator Ron Johnson of Wisconsin said he has "a hard time believing I'll have enough information for me to support a motion to proceed this week."

Senator Rand Paul of Kentucky said it would be worse to "pass a bad bill than to pass no bill."

Republicans can't afford more than two defections.

Additional uninsured

The 22 million additional people without coverage under the Senate proposal is slightly better than the 23 million who'd be left without insurance under the measure the House approved last month, the budget office has estimated. President Donald Trump has called the House version "mean" and called on Senate Republicans to approve legislation with more "heart."

Of the 22 million, 15 million of them would have no insurance next year under the bill, the nonpartisan budget office said. That could be a particular concern to Nevada Senator Dean Heller, who faces perhaps the toughest 2018 re-election race of any Senate Republican and who has said he can't support a health-care package that cuts Medicaid and takes coverage from "tens of millions of Americans and tens of thousands of Nevadans."

A total of 49 million Americans would be uninsured in 2026.

Republican Senator Susan Collins tweeted Monday: 'CBO says 22 million people lose insurance; Medicaid cuts hurt most vulnerable Americans; access to health care in rural areas threatened.' (Jason Burles/CBC)

The budget office report said it believes the Senate bill "would increase the number of uninsured people substantially. The increase would be disproportionately larger among older people with lower income" — especially those between 50 and 64 and with incomes below 200 per cent of the poverty level, or around $30,300 for a single person. Those ages are just shy of when people begin qualifying for Medicare coverage.

Penalty added for gap in coverage

Earlier Monday, Republican leaders added a penalty to their bill for people who've had at least a 63-day gap in coverage during the past year. Under that proposal, if they then buy insurance, they would face a six-month delay before it takes effect. The budget office said its estimate included the impact of that addition.

The change was aimed at helping insurance companies and the insurance market by discouraging healthy people from waiting to buy a policy until they get sick. Insurers need healthy customers who are inexpensive to cover to help pay the costs of people with medical conditions that are costly to treat.

The Senate bill would roll back much of Obama's health-care overhaul. His statute pressures people to buy insurance by imposing a tax penalty on those who don't, but the Republican legislation would repeal that penalty, effectively erasing Obama's so-called individual mandate.

The CBO estimates that enacting the Better Care Reconciliation Act would reduce the cumulative U.S. federal deficit by $321 billion over the next 10 years.

That's an additional $202 billion in savings compared with the bill passed by the House of Representatives.

The CBO estimates the Senate bill would reduce spending by $1.022 trillion and reduce revenues by $701 billion.

The budget office writes that, "The largest savings would come from reductions in outlays for Medicaid — spending on the program would decline in 2026 by 26 per cent in comparison with what CBO projects under current law," also known as Obamacare.

Repealing a tax on the wealthy

The CBO also says that the largest revenue reductions would come from "repealing a surtax on net investment income and repealing annual fees imposed on health insurers."

In a Facebook post last week, former president Barack Obama wrote that the Senate bill would lead to "a massive transfer of wealth from middle-class and poor families to the richest people in America. It hands enormous tax cuts to the rich and to the drug and insurance industries, paid for by cutting health care for everybody else."

The American Medical Association, the largest doctors' organization in the U.S., sent a letter Monday to Senate leaders saying the draft legislation violates the medical oath to "first, do no harm."

The doctors group says the Senate bill's Medicaid payment formulas threaten to "limit states' ability to address the health care needs of their most vulnerable citizens" and won't keep up with new medical innovations and epidemics such as the opioid addiction crisis.

The CBO also weighed in on what will happen to health insurance premiums.

"Under the Senate bill, average premiums for benchmark plans for single individuals would be about 20 per cent higher in 2018 than under current law, mainly because the penalty for not having insurance would be eliminated, inducing fewer comparatively healthy people to sign up, the CBO states in its estimate.