WASHINGTON — The Republican health plan speeding toward a vote as early as this week would increase the number of uninsured people by 22 million by 2026, the Congressional Budget Office estimated Monday, delivering a projection that immediately weighed on the unfolding debate and wavering senators.

The report from Congress' nonpartisan scorekeeper also estimated that the Senate plan to overhaul the Affordable Care Act would reduce the federal deficit by $321 billion over the next decade. The savings come largely from slashing expected Medicaid spending by $772 billion, although much of those savings would be consumed by tax cuts for the wealthy and insurers.

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Over time, insurance premiums would fall, but deductibles would rise and coverage would shrink, the CBO projected, ultimately leaving many to pay more for health care.

The analysis arrived just as Senate Republicans began a crucial week in the winding GOP effort to dismantle the health law pushed by former President Barack Obama, and as several urged their leaders to slow down. After the report came out, a key Republican, Maine's Susan Collins, wrote on Twitter that she would oppose a major procedural step, imperiling the quick action GOP leaders hoped for this week.

Senate conservatives are pushing for a more thorough repeal while moderates worry that the proposal goes too far, particularly in cutting spending on Medicaid, which provides health coverage to the poor and disabled. For some, the CBO report added to their worries and to Democratic attacks.

Republicans can afford to lose but two GOP votes to pass the bill through the Senate.

Sen. Bob Casey (D., Pa.) called the bill "obscene."

"Pennsylvania families will pay higher costs for less care with fewer protections … in order to lavish the wealthiest with tax cuts," Casey said in a statement.

The Democratic Senate leader, New Yorker Chuck Schumer, said Republicans should see the CBO report as "a giant stop sign."

Republicans were more muted. Senate Majority Leader Mitch McConnell (R., Ky.) issued a short statement saying "Americans need relief from the failed Obamacare law" and touting the projected cuts in taxes, the deficit and insurance premiums.

"The Senate should proceed carefully, avoid overreacting to questionable predictions, and stay focused on delivering on our promise to move health care in a more consumer-driven, sustainable direction on behalf of the millions of Americans who have been harmed by Obamacare's broken promises," Sen Pat Toomey (R., Pa.) said in a statement.

McConnell is eager to advance the bill before lawmakers return home for a July 4 recess, when they might face intense pressure from groups pushing against the proposal, and he still has a few days to maneuver and press for votes.

But the estimate provides a new hurdle.

Overall, 49 million people would be uninsured by 2026, the CBO estimated, compared with 28 million under current law. Some of the impact comes fast: 15 million more would be uninsured next year. By 2026, around 15 million fewer would be enrolled in Medicaid.

Insurance premiums would rise at first but then fall — by 20 percent, on average, for individuals by 2026 — but the plans would cover fewer benefits, and deductibles would increase, the CBO estimated. Most individuals buying their own insurance "would have higher out-of-pocket spending on health care than under current law," the analysts projected. Deductibles would cost so much that "few low-income people would purchase any plan."

Republicans have long bemoaned the high deductibles under the existing law as they argued that they had no choice but to revamp the law often called Obamacare. They have also criticized the CBO's accuracy, although the office has long been considered the official analyst on Capitol Hill.

It estimated that impacts of the GOP bill would vary across age and income, and depend on how much coverage people buy.

A 40-year-old making $11,400 a year, for example, would pay $5,200 less for a "bronze" plan, the bottom tier on the Affordable Care Act exchanges, once a boost in his tax credits was factored in. But a 64-year-old with a $56,800 income buying a "silver plan," the second tier, would see an added cost of nearly $14,000 more per year for his premium, due largely to losing an existing tax credit.

The Senate plan, largely building on the bill the GOP-led House approved in May, saves more money — about $200 billion worth — and leaves a million fewer people uninsured, according to the CBO.

Republicans argue that a more conservative, free-market approach will help lower premiums and rescue the country from what they describe as an imploding health system riddled with rising premiums. Democrats say the GOP proposals will lead to fewer people with insurance and strip vital consumer protections, including rules that bar insurers from charging more for people with expensive pre-existing conditions, such as cancer or diabetes.

Business groups such as the U.S. Chamber of Commerce and some major insurers support the GOP proposal, but a raft of medical groups, including the American Medical Association and American Cancer Society, have spoken out against it.

"Congress should be working to increase the number of Americans with access to quality, affordable health insurance instead of pursuing policies that have the opposite effect," the AMA wrote Monday in a letter to Senate leaders.

Both the House and Senate GOP plans roll back many of the taxes and mandates that underpin the Affordable Care Act, including levies on people with high incomes and on health-care companies and an unpopular requirement that everyone obtain insurance. The proposals also end the promise that the federal government would pay 90 percent of the costs for newly eligible Medicaid recipients — forcing states like Pennsylvania and New Jersey to either come up with billions of dollars themselves or cut services — though the Senate plan would scale back the funding more slowly.

The Senate version also would tie future Medicaid funding to a less generous inflation index, further reducing expected federal aid to states. Fiscal conservatives say Medicaid spending has to be controlled to make the program sustainable, but Democrats and some Republicans argue that the changes would force cuts in benefits or coverage.

At stake is funding that has helped more than one million people in Pennsylvania and New Jersey obtain Medicaid coverage, along with millions of others in 29 other states and the District of Columbia. In Pennsylvania, the House bill would cost the state $26 billion over nine years, Gov. Wolf wrote in May, and the Senate bill would go further in the long run.

Both the Senate and House plans, in different ways, would allow states to weaken requirements that insurers cover "essential health benefits" like maternity care, substance abuse treatment and prescription drug purchases. To Republicans this will help lower costs, but Democrats say vital services could become prohibitively expensive.

The GOP bills both eliminate funding to Planned Parenthood and allow insurers to charge older consumers five times more than younger ones, instead of three times more.