* Senate Finance Committee to hold hearing Monday
* Republican moderate worries about impact on Medicaid (Adds revised bill released)
WASHINGTON, Sept 25 (Reuters) - U.S. senators made a last-ditch effort on Monday to secure support for the latest Republican attempt to repeal former President Barack Obama's signature healthcare law, releasing revised legislation to appeal to undecided senators.
The bill had faced possible defeat this week as several senators in the party voiced concerns.
The 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 criticism that the measure has not been thoroughly vetted.
Republican senators leading the effort on Monday released a revised version of their bill, originally introduced by Senators Lindsey Graham and Bill Cassidy. It included a table that said some states where senators have been undecided, such as Alaska and Maine, would do better under the bill than under current law. The Washington Post first reported the revision.
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.
Democratic leaders roundly rejected the revised draft 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.
The Graham-Cassidy bill 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 undoing Obamacare will mean millions lose healthcare, including some with pre-existing medical conditions.
The non-partisan Congressional Budget Office is expected to produce as early as Monday a preliminary analysis of the bill that would assess its impact on budget deficits.
More time is likely needed for the CBO to gauge how the bill could affect Americans' access to health insurance.
Opposition to the Graham-Cassidy plan grew on Sunday.
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, who voted against her party's bill in July, said on CNN's "State of the Union" on Sunday that it was difficult 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.
It was unclear whether the revisions would sway the Republican holdouts.
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."
A total of three Republican defections would kill off the latest effort to repeal Obamacare. Republican Senators John McCain and Rand Paul already have registered their opposition. (Reporting by Susan Cornwell and Richard Cowan; Editing by Mary Milliken and Bill Trott)