NBC NEWS - The Republican plan to replace the Affordable Care Act would leave 24 million more Americans without health insurance by 2026 than under current law, according to an analysis Monday from the Congressional Budget Office.

The CBO report found that 14 million more people would be without health insurance by 2018.

Following a two-year spike, the plan would also lower average premiums after 2020 relative to President Barack Obama's healthcare law. But premiums would be expected to go down for younger people, while being raised for older Americans.

The CBO also estimated that the GOP legislation would reduce federal deficits by $337 billion by by 2026.

Republicans have been bracing for the estimate ahead of the CBO's release. The GOP plan's elimination of the government requirement to purchase insurance all but guaranteed the projection that fewer Americans would be covered.

"The one thing I'm certain will happen is CBO will say, 'Well, gosh, not as many people will get coverage.' You know why? Because this isn't a government mandate,'" House Speaker Paul Ryan said on CBS News on Sunday.

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Advocates of the bill preemptively dismissed the CBO report, saying the government entity was ill-equipped to grade legislation with such a massive scope.

"I love the folks at the CBO, they work really hard. They do. Sometimes we ask them to do stuff that they're not capable of doing," White House Office of Management and Budget director Mick Mulvaney said on ABC News on Sunday.

The projection only further complicates the already shaky chances the legislation passes. Democrats stand ready to pounce on GOP lawmakers for advocating for a plan that could lead to less Americans having health insurance. Conservative members of Congress, however, oppose the legislation for not quickly enough repealing the major tenets of Obama's healthcare law, like Medicaid benefits.

"I firmly believe that nobody will be worse off financially in the process that we're going through," Secretary of Health and Human Services Tom Price said on NBC's "Meet The Press" on Sunday. "They'll have choices that they can select the kind of coverage that they want for themselves and for their family, not the government forces them to buy."