"The public statements and tweets ... make it impossible to do my job and to assure the courts and the prosecutors in the department that we are doing our work with integrity," Barr told ABC News.

Further raising questions about Barr's role, Trump tweeted on Wednesday praising the attorney general for "taking charge” of the case — despite the attorney general having not weighed in on it publicly.

McConnell declined to say on Thursday if he thought Trump's tweets on the Stone case were "inappropriate," instead turning the conversation back to Barr.

"The attorney general has said it's making it difficult for him to do his job. I think the president ought to listen to the attorney general. ...The president made a wise selection in picking Bill Barr. I think he ought to listen to him," McConnell added.