* Senate Finance Committee to hold hearing Monday
* Republican moderate worries about impact on Medicaid
WASHINGTON, Sept 25 (Reuters) - The latest Republican effort to repeal former U.S. President Barack Obama's signature healthcare law faced possible defeat this week as several senators in the party voiced concerns about the bill under consideration.
The U.S. Senate is up against a Saturday deadline for deciding the fate of the 2010 Affordable Care Act, popularly known as Obamacare, because of an expiring rule that lets the Republican healthcare legislation pass with just a simple 51-vote majority, instead of the 60-vote threshold needed for most measures.
Republicans, who control the Senate 52-48, were finding it difficult even to clear that lower hurdle.
The Senate Finance Committee is scheduled to hold a hearing on Monday in an attempt to build support for the bill and to tamp down Democratic criticisms the measure has not been thoroughly vetted.
Republican senators leading the effort plan to release a revised version of their bill that would send more money to Alaska and Maine, the states of two holdout senators, the Washington Post reported late on Sunday.
For seven years, Republicans have hammered Obamacare as an unwarranted and overly expensive government intrusion into American healthcare. Republican President Donald Trump made repealing Obamacare one of his top campaign promises in 2016. Democrats have fiercely defended it, saying it has extended health insurance to millions.
The most previous attempt to repeal Obamacare fell one vote short in July, in a humiliating setback for Trump and Senate Majority Leader Mitch McConnell.
Opposition grew on Sunday to the plan by Senators Lindsey Graham and Bill Cassidy that could be up for a vote on the Senate floor this week.
It would take federal money spent on the Medicaid program for the poor and disabled, as well as subsidies to help Americans buy private insurance, and divvy it up to the states in block grants. Advocates say that would give states more discretion to manage their own healthcare schemes.
Opponents fear that millions would lose healthcare, including some with pre-existing medical conditions.
Conservative Republican Senator Ted Cruz, speaking at an event in his home state of Texas, warned on Sunday that Trump and McConnell could not count on his vote. Cruz has pushed for greater government cost savings in healthcare.
Moderate Republican Senator Susan Collins of Maine, interviewed on CNN's "State of the Union" on Sunday, said it was difficult for her to "envision a scenario where I would end up voting for this bill."
She worried about cuts to Medicaid benefits to the poor and disabled.
U.S. Senate Democratic leader Chuck Schumer dismissed the late effort to revise the bill and add money for a few states, calling it "just as bad for those states and the rest of the states because it still contains a massive cut to Medicaid."
GRAHAM VOWS TO KEEP UP EFFORT
A total of three Republican defections would kill off the latest effort to repeal Obamacare. Republican Senators John McCain and Rand Paul have already registered their opposition.
As early as Monday, the non-partisan Congressional Budget Office is expected to produce a preliminary analysis of Graham-Cassidy that would assess the bill's impact on budget deficits.
More time is likely needed for the CBO to gauge how the bill could affect Americans' access to health insurance.
Despite the deepening skepticism, Graham pledged on Sunday to keep pushing for passage. During an interview on ABC, Graham said that if his bill was defeated, he would aim to use his seat on the Senate Budget Committee to keep the effort alive.
An aide to Graham said in an email that the senator was suggesting an extension of the Sept. 30 deadline. That could create complications for tax overhaul legislation that Trump also is pushing.
Independent analyzes indicate Graham-Cassidy would fundamentally redistribute federal healthcare money, generally with Republican-leaning states benefiting and Democratic-leaning states losing.
State-by-state impacts from Graham-Cassidy would vary, but some of the states whose senators are undecided would stand to lose funding, the Axios news website reported on Friday, citing a study by the Centers for Medicare and Medicaid Services, a unit of the Department of Health and Human Services that oversees Medicaid and the Obamacare program.
The CMS study found that by 2026, Alaska would lose 38 percent of its federal funding for insurance subsidies and Medicaid. Both of Alaska's Republican senators, Lisa Murkowski and Dan Sullivan, are still on the fence over Graham-Cassidy.
The insurance industry, hospitals, medical advocacy groups such as the American Medical Association, American Heart Association and American Cancer Society, the AARP advocacy group for the elderly and consumer activists oppose the bill. (Reporting by Susan Cornwell and Richard Cowan; Editing by Peter Cooney and Mary Milliken)