Sen. Brian Nieves, R-Washington, said the changes made by Rep. Doug Funderburk, R-St. Peters, and members of the House were different from what was agreed on.
Nieves said the changes were so great that the House had essentially eliminated any chance of the bill passing the Senate in its present form.
"They made such a gigantic change by adding an entirely new provision," Nieves said. "It's just too far away from what any original intention of that bill was."
House Majority Leader John Diehl, R-St. Louis County, wasn't optimistic that further discussion on the differences would prove useful.
"I don't think [Funderburk] is willing to cede from his point." Diehl said.
Funderburk was not at the capitol on Thursday due to a family matter.
A similar bill was passed in 2013, but was vetoed by Governor Jay Nixon. The veto was overriden by House Republicans but failed in the Senate by two votes.
Lawmakers have until 6pm on Friday to reconcile any differences between the two verisons of the bill.