Republican senators struggled to gather more support for a last-ditch attempt to repeal Obamacare despite revising funding provisions of their bill to make it more attractive to some representatives.
The outcome remained in doubt with several senators in the party voicing concerns in recent days about the legislation to dismantle Democratic former President Barack Obama's signature healthcare law.
In hopes of finding more backing, Republican senators leading the effort released a changed version of their bill that included a table showing some states where senators have been undecided, such as Alaska and Maine, would get more money.
For seven years, Republicans have hammered Obamacare, which extended health insurance to some 20 million Americans, as an unwarranted and costly government intrusion into healthcare, while also opposing taxes it imposed on the wealthy.
President Donald Trump made repealing Obamacare one of his top campaign promises in 2016. Democrats have fiercely defended it.
A Senate Finance Committee hearing on the healthcare legislation on Monday was disrupted by protesters chanting "No cuts for Medicaid, save our liberty." Capitol Hill police removed the protesters, many in wheelchairs, from the hearing room.
A total of three Republican defections would kill off the latest anti-Obamacare effort.
Republican Senators John McCain, Rand Paul and Ted Cruz have said in recent days they would vote no. Other senators such as Susan Collins and Lisa Murkowski have also voiced reservations.
A spokesman for Paul said on Monday the senator still opposes the latest version despite the tweaks and an aide for Cruz said on Monday that the Texas conservative still opposes the bill.
Trump said there was little room for Republican wavering on healthcare.
"We have 52 senators, so you lose two, you're out," he told the Alabama-based "Rick and Bubba" radio program on Monday.
"We don't have much a margin. We don't have any margin."
Democratic leaders roundly rejected the revised draft of the repeal legislation as a sleight of hand to gain support.
The last attempt to repeal Obamacare fell one vote short in July, in a humiliating setback for Trump and Senate Majority Leader Mitch McConnell.
