Washington (CNN) Chief Justice John Roberts, who is presiding over the impeachment trial of President Donald Trump, scolded both the Democratic House managers and the President's defense team early Wednesday morning after a contentious exchange on the Senate floor.

The extraordinary moment capped an acrimonious opening to Trump's impeachment trial, and placed Roberts, who otherwise largely handled procedural tasks on day 1, in the position of reminding advocates for both sides to maintain decorum during a highly partisan affair.

"I think it is appropriate for me to admonish both the House managers and the President's counsel in equal terms to remember that they are addressing the world's greatest deliberative body," Roberts said. "One reason it has earned that title is because its members avoid speaking in a manner and using language that is not conducive to civil discourse."

Roberts had just listened to the impeachment managers and Trump's legal team rip into each other after House Judiciary Chairman Jerry Nadler made the case for issuing a subpoena for former national security adviser John Bolton's testimony.

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