US Republicans' long-awaited plan to replace former President Barack Obama's health law is facing opposition from members of their own party.
House committees plan to begin voting on the legislation - which would repeal penalties for those who do not buy health insurance - on Wednesday.
But congressional Republicans have been saying the plan goes too far or doesn't go far enough.
Conservative critics have dismissed it as "Obamacare 2.0" or "Obamacare Lite".
The Affordable Care Act, known as Obamacare, helped 20 million previously uninsured Americans get health insurance.
However, increases in insurance premiums - which were also a problem before the health law - have irked many Americans.
What is the Republican plan?
The proposal unveiled on Monday would preserve some popular elements of the existing law, including allowing young people to remain on their parents' insurance plans until the age of 26.
The ban on insurers denying coverage to those with pre-existing conditions would remain in place.
But the plan is expected to cover fewer people than those who gained insurance under the Affordable Care Act.
While penalties for those who don't buy health insurance would be scrapped, those who let their coverage lapse could see their insurance premiums raised by 30 percent.
The Republican legislation would limit future federal funding for Medicaid, which covers low-income people.
Nearly half of the Americans who gained healthcare coverage under Obamacare received it through the expansion of Medicaid, which would end in 2020 under the new plan.
The proposal would also eliminate subsidies for those with modest incomes, replacing them with age-based tax credits to mitigate the cost of premiums.
House Speaker Paul Ryan said the bill would "drive down costs, encourage competition, and give every American access to quality, affordable health insurance".
What are Republican critics saying?
Republican leaders are embarking on a bid to win their membership over to what President Donald Trump described in a tweet on Tuesday as "our wonderful new Healthcare Bill".
But four Republican senators have already said the plan does not adequately protect low-income people who received Medicaid coverage under the Affordable Care Act.
They are Rob Portman of Ohio, Shelley Moore Capito of West Virginia, Cory Gardner of Colorado and Lisa Murkowski of Alaska.
Three other, conservative Republican senators have suggested the plan does not go far enough in abolishing Obamacare.
They are Mike Lee of Utah, Rand Paul of Kentucky and Ted Cruz of Texas.
Mr Paul tweeted: "This sure looks like Obamacare Lite!"
Members of the House Freedom Caucus, a rump of about 30 hardliners, have also sounded sceptical.
Mr Trump was scheduled to meet with House members who are monitoring support for the new plan on Tuesday.
Meanwhile, House Oversight Committee chairman Jason Chaffetz has been savaged on social media for saying Americans need to choose between a new smartphone and medical insurance.
He told CNN: "And so maybe, rather than getting that new iPhone that they just love and they want to spend hundreds of dollars on, maybe they should invest in their own healthcare."