Colorado Sen. Cory Gardner has indicated he will vote against any Democratic measure to force additional witnesses in the Senate impeachment trial of President Trump.

“I do not believe we need to hear from an 18th witness," Gardner, a Republican, told Colorado Politics. "I have approached every aspect of this grave constitutional duty with the respect and attention required by law, and have reached this decision after carefully weighing the House managers and defense arguments and closely reviewing the evidence from the House, which included well over 100 hours of testimony from 17 witnesses.”

Gardner is one of a handful of moderate Republicans who Democrats are aiming to convince to vote with them to call more witnesses in the trial.

Democrats need four Republican votes in order to force additional witness testimony. Senate Majority Leader Mitch McConnell told the Republican caucus late Tuesday he did not yet have the votes to kill a Democratic resolution to call witnesses.

A vote on the matter is expected Friday.