Senate Republicans have released their long-awaited bill to dismantle much of Barack Obama's healthcare law.
The plans include proposing to cut Medicaid for low-income Americans and erase tax boosts that Mr Obama imposed on high earners and medical companies to finance his expansion of coverage.
The bill would provide tax credits to help people buy insurance and would also let states get waivers to ignore some coverage standards that Obamacare requires of insurers.
The measure represents the Senate Republicans' effort to achieve a top tier priority for President Donald Trump and virtually all Republican members of Congress.
Mr Trump expressed hope that the Senate would pass the healthcare plan "with heart".
The bill faces broad opposition from Democrats but Mr Trump said that Republicans would love to have Democratic support.
Senate Majority Leader Mitch McConnell hopes to push it through his chamber next week.
Yet it faces an uncertain fate in the Senate.
At least half a dozen Republican senators - conservatives as well as moderates - have complained about the proposal, the secrecy with which Mr McConnell drafted it and the speed with which he would like to whisk it to passage.
Facing unanimous Democratic opposition, the bill would fail if just three of the Senate's 52 Republican senators oppose it.
The measure would provide $50bn (€44.8bn) over the next four years that states could use in an effort to shore up insurance markets around the country.
For the next two years, it would also provide money that insurers use to help lower out-of-pocket costs for millions of lower income people.
Mr Trump has been threatening to discontinue those payments, and some insurance companies have cited uncertainty over those funds as reasons why they are abandoning some markets and boosting premiums.
The House approved its version of the bill last month.
Democrats say Republican characterisations of Mr Obama's law as failing are wrong and add that the Republican plan would boot millions off coverage and leave others facing higher out-of-pocket costs.
The non-partisan Congressional Budget Office said the House bill would cause 23 million people to lose coverage by 2026.
The budget office's analysis of the Senate measure is expected in the next few days.