Senate Majority Leader Mitch McConnell (R-Ky.) left the door open for Republicans to call key witnesses, including Hunter Biden, in the upcoming Senate impeachment trial against President Donald Trump, NBC News reported Tuesday.

Speaking with reporters Tuesday afternoon, McConnell remarked that if witnesses are called, "I can't imagine" only the Democrats having people they would like to hear from appear before Congress.

In other words, if those who favor impeachment call someone they believe will help the case against Trump, such as former national security adviser John Bolton, it can be expected that those opposed to impeachment would be able to call on witness of their own, including Hunter Biden, who Republicans believe has relevant information validating Trump's concern about corruption in Ukraine involving former Vice President Joe Biden.

NBC News Capitol Hill correspondent Kasie Hunt broke the news when she asked McConnell whether he would back calling Hunter Biden to the witness stand, as Sen. Rand Paul (R-Ky.) has recently suggested.

McConnell's comments came just hours after he knocked talk of calling additional impeachment witnesses, saying the need to call for more witnesses shows the impeachment case to be particularly weak.

"If the existing case is strong, there's no need for the judge and the jury to reopen the investigation. If the existing case is weak, House Democrats should not have impeached in the first place," McConnell said from the Senate floor, according to The Hill.

On Monday, Politico reported that GOP senators are at odds over how to handle the calling of witnesses in the upcoming trial, many weighing a vote in favor of calling witnesses despite McConnell's wishes.

Sen. Paul reportedly warned Republican colleagues at a party lunch last week, saying, "Don't think you can just vote for Bolton and not the witnesses Trump wants."

The GOP will need to decide rather quickly how to proceed as McConnell confirmed that "in all likelihood" the Senate impeachment trial would begin Jan. 21.