His comments come after Kelly defended Lt. Col. Alexander Vindman, who was among administration officials who raised concerns about Trump, which spurred the impeachment trial.

The Senate Democratic leader's letter comes amid President Donald Trump's ouster of key government officials in the impeachment probe.

Republicans who control the Senate said there was a chance the trial could end on Friday with Trump's acquittal, leaving him in office and rendering moot the articles of impeachment.

The articles of impeachment against United States President Donald Trump don’t move to the Senate by themselves.

The jockeying between chambers over procedure has largely focused on a still unsettled dispute about witnesses.

It’s now more than three weeks since the House impeached Trump on charges of abuse and obstruction.

Bolton said that after "careful consideration and study'' he decided that he would comply with a Senate subpoena.

Trump has long seen a Senate trial, where he is almost certain to be acquitted, as an opportunity for vindication.

Trump has been among Roberts’ critics, blasting the chief justice for his health care votes.

The U.S. House Speaker says that before she sends the articles of impeachment approved against Trump to the Senate, GOP leaders must provide more detail about how they will handle the expected trial.