"So I say to the Republican leadership: What are you afraid of? Bring that bill out," Sanders, who is also a member of Democratic leadership,  said from the Senate floor. 
Sanders added that GOP senators "should be embarrassed" by the secretive process to hash out ObamaCare repeal-and-replace legislation, and lawmakers need to have a "series of hearings." 
"It should tell you something that major, major legislation is being written at this moment and most Republicans don't have a clue what's in that legislation," he said. 
Sanders's speech comes as Democrats take over the Senate floor on Monday evening to protest the GOP's closed-door effort, with Republicans expected to force a vote on legislation as soon as next week. 
Sanders, like other Democratic senators, compared the months of public haggling over the Affordable Care Act to the current legislative effort, in which GOP senators are discussing their forthcoming proposal during a string of closed-door meetings. 
"I find it amazing that those same Republicans seem to think it's OK for legislation to be written behind closed doors and not have one single committee hearing," Sanders said. 
Sanders urged every Democratic senator to fight "in an unprecedented way" to help stop the GOP legislation. 
"Our job right now is to make sure that this disastrous Republican proposal never sees the light of day," he said. 
No Democratic senator is expected to support the GOP legislation, but they don't have the ability to block the bill on their own. Republicans have 52 seats. They can afford to lose two GOP senators and still have Vice President Pence break a tie. 
Democrats are stepping up their effort to publicly push back against the GOP legislation. Senate Minority Leader Charles SchumerChuck SchumerManchin meeting with Biden, Schumer in Delaware Progressives' optimism for large reforms dwindles Democratic frustration with Sinema rises MORE (D-N.Y.) said from the Senate floor earlier that Democrats are willing to gum up the procedure in the chamber to keep the bill from passing. 
Sanders held a Facebook Live event with Sen. Elizabeth WarrenElizabeth WarrenDems look to keep tax on billionaires in spending bill Six big off-year elections you might be missing Republican spin on Biden is off the mark MORE (D-Mass.) earlier Monday, noting he would reintroduce a single-payer healthcare bill. 
"I would hope that we would come forward, as a nation, and join every other country on Earth ... and say that healthcare is a right of all people, not a privilege," he added from the Senate floor.  
"I think we'll have ample opportunity to read and amend the bill," McConnell said when pressed on whether lawmakers would have at least 10 hours to review the bill.