Top Senate Republican Mitch McConnell has denounced US President Joe Biden’s voting rights speech as “incoherent” and “profoundly unpresidential”.
The remarks come one day after Mr Biden delivered a fiery speech in Atlanta calling for an overhaul of the US election system.
The president said he supported changes that would allow his party’s proposed overhaul of the election system to be passed without the support of opposition Republicans.
Currently, a majority of 60% is needed to pass most legislation in the Senate.
Mr Biden said the push to pass the legislation was a “battle for the soul of America”, adding that the 60-vote rule – known as the filibuster – had rendered the Senate “a shell of its former self”.
Addressing his colleagues in Washington on Wednesday, the Kentucky Republican senator slammed Mr Biden’s comments as a “rant” that was “incoherent, incorrect, and beneath his office”.
Even Biden ally and Democratic Illinois Senator Dick Durbin conceded that the president’s tone may have been overheated.
Meanwhile, former President Barack Obama threw his weight behind Mr Biden’s calls to scrap the filibuster.
Senate Democrats plan to vote on the Freedom to Vote Act and the John Lewis Voting Rights Advancement Act by Monday.
If they fail to pass, as expected, the Senate will begin to consider changing filibuster rules.