* Trump endorses bill, but it is unclear it can pass Senate
* Comedian Kimmel calls bill co-sponsor Cassidy a liar
* Group forecasts big federal funding cuts to states (Adds Trump tweet on pre-existing conditions, senators' positions)
WASHINGTON, Sept 20 (Reuters) - Senate Republicans announced plans to vote next week on their latest bid to scuttle Obamacare even as a popular comedian who has become part of the U.S. healthcare debate denounced the bill and former President Barack Obama on Wednesday warned of "real human suffering."
President Donald Trump, who has expressed frustration at the Senate's failure thus far to pass legislation dismantling Obama's signature legislative achievement, said "47 or 48" Republicans back the bill, which needs 50 votes for passage in the 100-seat Senate, which his party controls 52-48.
"We think this has a very good chance," Trump, who made replacing Obamacare a top 2016 campaign promise, told reporters during an appearance with Egypt's president in New York.
As they worked to gather enough votes to win after prior legislation failed in July, congressional Republicans and the White House were on the defensive after Jimmy Kimmel used his late-night TV show to blast the proposal and call Republican Senator Bill Cassidy, one of its two sponsors, a liar.
"This guy, Bill Cassidy, just lied right to my face," Kimmel said on his show on Tuesday night, referring to the senator who since May had touted a "Jimmy Kimmel test" of standards any Obamacare replacement would need to possess.
Senate Majority Leader Mitch McConnell, who was noncommittal on Tuesday about scheduling a vote, now intends to bring it to the Senate floor next week, said his spokesman David Popp.
Republicans are using the measure Cassidy is sponsoring with fellow Senator Lindsey Graham to make one last push this year to pass legislation to roll back the 2010 Obamacare law, a goal of theirs for seven years, facing a Sept. 30 deadline.
Avalere Health, a healthcare consultancy to hospitals and insurers, forecast that the bill would slash federal funding to states by $215 billion through 2026, with 34 states facing cuts.
Hit hard would be Democratic-governed California and New York, which expanded the Medicaid insurance program for the poor and disabled under Obamacare, while Republican-governed Texas, which did not expand Medicaid, would be a winner, Avalere said.
It remained unclear if the bill, opposed by Democrats and top medical groups and hospitals, can attract the 50 votes needed for passage, with Vice President Mike Pence ready to cast a tie-breaking vote.
Kentucky Senator Rand Paul opposes the bill. Three other Republicans have said they are still evaluating it: Susan Collins of Maine, Lisa Murkowski of Alaska and John McCain of Arizona. The Topeka Capital-Journal newspaper reported on Wednesday that Republican Jerry Moran of Kansas was undecided on the bill, citing a statement from his office.
In a speech in New York, Obama defended the Affordable Care Act, known informally as Obamacare, which expanded medical insurance to 20 million Americans.
"So when I see people trying to undo that hard-won progress for the 50th or 60th time, with bills that would raise costs or reduce coverage or roll back protections for older Americans or people with pre-existing conditions ... it is aggravating," the Democratic former president said.
"And it's certainly frustrating to have to mobilize every couple of months to keep our leaders from inflicting real human suffering on our constituents."
Cassidy defended his bill, which would divvy up healthcare money as block grants to states, let them opt out of some Obamacare consumer protections and waive requirements that insurers cover certain benefits. It also would end Obamacare's Medicaid expansion.
Kimmel entered the healthcare debate after revealing on his show in May that his newborn son had undergone life-saving emergency surgery for a congenital heart condition, and pleaded that no family be denied medical care because they cannot afford it. Cassidy appeared that month on "Jimmy Kimmel Live!"
"He said he would only support a healthcare bill that made sure a child like mine would get the health coverage he needs no matter how much money his parents make," Kimmel said on Tuesday.
"Stop using my name, OK? Because I don't want my name on it. There's a new 'Jimmy Kimmel test' for you. It's called the lie detector test. You're welcome to stop by the studio and take it any time," he said to cheers from his audience.
Cassidy, a gastroenterologist who represents Louisiana, gave a measured response to Kimmel's remarks, telling reporters on Capitol Hill, "It was a personal attack and I can't help that."
Graham blasted the comedian.
"I bet he looked at some liberal talking point, bought it hook, line and sinker, and went after Bill Cassidy without talking to him. And I think that's unfair," Graham said on Fox News Channel's "Fox & Friends" show.
Cassidy said his proposal would protect people who are already ill, although it does let states waive an Obamacare mandate that insurers cannot charge people who have pre-existing medical conditions more than those who are healthy.
"There is a specific provision that says that if a state applies for a waiver, it must ensure that those with pre-existing conditions have affordable and adequate coverage," Cassidy told CNN.
Trump, in a tweet late on Wednesday, said he would not sign the bill if it did not include coverage of pre-existing conditions. "It does! A great bill," Trump said.
(Additional reporting by Jeff Mason, Steve Holland, Eric Walsh, Justin Mitchell, Yasmeen Abutaleb and Roberta Rampton; Writing by Will Dunham; Editing by Bill Trott and Jonathan Oatis)