WASHINGTON – House Republicans will Tuesday unveil a long-term budget plan that essentially privatizes Medicare, a move that is sure to draw ire from progressives on Capitol Hill.

The proposal, authored by House Budget Committee Chairman Paul Ryan (R-WI), aims to cut $4 trillion in federal spending over ten years, in part by ending Medicare as we know it for Americans who are currently under the age of 55.

Those nearing retirement within the next 10 years will be covered by single-payer program, which pays the medical expenses of seniors. The rest would have to choose from a series of private insurance plans to cover them when they turn 65, according to previews of the proposal. The federal government would pay roughly the first $15,000 in costs; after that, they're on their own.

"There is nobody saying that Medicare can stay in its current path," Ryan said on Fox News Sunday. "We should not be measuring ourselves against some mythical future of Medicare that isn't sustainable."

The proposal also cuts Medicaid, which helps pay health care expenses for low-income Americans. Currently a joint program run by the federal government and states, the Ryan plan would turn it into a series of block grants for states, considerably reducing benefits.

House progressives declined to comment on the plan as it had not been officially unveiled, but it's certain to bring about a rancorous debate over whether to balance the budget by cutting into the safety net. Though both parties agree that health care costs are a major driver of federal spending, liberals have argued that seniors and low-income people should not have to pick up the tab for a deficit caused largely by tax cuts, two unfunded wars and a recession.

A new NBC/Wall Street Journal poll found Monday that 76 percent of Americans consider it unacceptable to cut Medicare, while 67 oppose cutting Medicaid, despite their deficit concerns.