WASHINGTON — A bill the Senate plans to vote on next week to repeal parts of Obamacare without a replacement would make the insurance market unstable, raise premiums and increase by 32 million the number of uninsured people, according to an analysis released Wednesday by the non-partisan Congressional Budget Office.

While repealing billions of dollars in taxes imposed under Obamacare to pay for expanding health coverage to millions more Americans, the legislation would still decrease deficits by $473 billion over 10 years because of the spending reductions.

The repeal bill is similar to one approved by the House and Senate in 2015 but vetoed by then-president Barack Obama.

The legislation would immediately end the Affordable Care Act mandates for people to obtain insurance and employers to offer it and also scrap in 2020 the federal subsidies to help people pay for coverage. But it would keep the regulations on what insurers have to cover and the requirement that they not turn down sick people seeking coverage or base premiums on their health status.

As a result, the pool of people buying insurance would be older and sicker, prompting insurers to increase premiums. Insurance plans could cost about 50% more right after subsidies are eliminated and could double in 10 years, the CBO estimated.

The White House and congressional Republicans have pushed back on CBO health care estimates as Congress has considered various proposals. In a statement Wednesday night, the White House responded to the latest analysis: "We continue to believe that CBO’s methodology is flawed, and this score fails to take into account the President’s full plan, which includes a replacement for Obamacare and administrative actions to reduce costs and expand access to quality, affordable care."

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CBO predicts that under the repeal proposal, faced with fewer customers with higher expenses, some insurers would likely stop selling plans. About half the country could have no option in the first year after subsidies are eliminated. After 10 years, three out of four Americans might not be able to buy a plan on the individual market, according to the CBO. “That's a true death spiral,” tweeted Larry Levitt, senior vice president at the Kaiser Family Foundation.

The bill would also end in two years the extra federal funding the ACA made available to states to expand eligibility for Medicaid to those earning slightly more than the poverty level. But unlike the bill the House passed and the Senate was unable to bring up, a repeal bill would not reduce federal support for traditional Medicaid.

Still, the rollback of Medicaid expansion is expected to significantly increase the number of people without health insurance.

CBO concludes that because of both the Medicaid cuts and elimination of private insurance subsidies for people who don’t get coverage through an employer, the number of people who are uninsured would rise by 32 million in 10 years.

By 2026, about 21% of Americans under age 65 could be without insurance, compared with a projected 10% if the ACA remains in place.

Republicans say the bill's two-year delay before the insurance subsidies and Medicaid funding are repealed would give Congress time to come up with an alternative program. But they have so far been unable to agree on what that might be. Two versions of a bill that would repeal parts of the the ACA and change some other provisions have not won enough GOP support to move to the floor over the past several weeks. Those bills would also result in millions more Americans not having insurance, according to CBO estimates.

GOP leadership still had not decided Wednesday which version of the bill would be voted on next week, but Senate Majority Leader Mitch McConnell, R-Ky., contended that it would be better to pass an overhaul than a straight repeal. Administration officials headed to Capitol Hill on Wednesday night to huddle with Republican senators to see whether a deal on a repeal-and-replace bill could be worked out.

“I think we all agree it’s better to both repeal and replace, but we could have a vote on either,” McConnell said at the White House on Wednesday. It is not clear McConnell has enough Republican support to bring a repeal-only bill to the floor, as three of the 52 GOP senators have already said they would oppose even debating such a bill and agreement by 50 senators is required to bring up any measure.

Tennessee Sen. Bob Corker told reporters that lawmakers were concerned about the brain cancer diagnosis of Sen. John McCain, R-Ariz., which was announced Wednesday, but acknowledged that "the math" also would be difficult if the Arizona senator was out since he was assumed to be a "yes" vote on the bill.

"We had a very substantive discussion," Corker said about the meeting of Republican lawmakers Wednesday night, but wouldn't go into detail. Corker is not one of the lawmakers of concern on the bill.

Calling the latest version “repeal and run,” Senate Minority Leader Chuck Schumer, D-N.Y., said the CBO analysis shows it’s a horrible idea.

“President Trump and Republicans have repeatedly promised to lower premiums and increase coverage, yet each proposal they offer would do the opposite,” Schumer said in a statement.

Like the earlier versions, the bill would block Planned Parenthood from receiving Medicaid funding for a year. The federal government already prevents Medicaid patients from receiving abortion services. But the bill would also block them from using Planned Parenthood for contraception, testing for and treatment of sexually transmitted diseases, and other services.

The taxes and fees the bill would repeal or delay include those the ACA imposed on investment income, higher earnings, tanning beds, sectors of the health care industry and on high-cost employer-provided insurance plans.

Contributing: Eliza Collins