Washington (CNN) Sen. Mark Warner, the top Democrat on the Senate Intelligence Committee, said Wednesday that the firing of Justice Department special counsel Robert Mueller would be a "gross abuse of power" and called for Congress to respond with "significant consequences" if President Donald Trump took that step.

Warner, a Virginia Democrat, took to the Senate floor for a speech, in which he said the firing of Mueller or the pardoning of those charged in the special counsel's investigation would represent crossing his "red line."

"Any attempt by this President to remove special counsel Mueller from his position or to pardon key witnesses in any effort to shield them from accountability or shut down the investigation would be a gross abuse of power and a flagrant violation of executive branch responsibilities and authorities," Warner said. "These truly are red lines and simply cannot allow them to be crossed."

"Congress must make clear to the President that firing the special counsel or interfering with his investigation by issuing pardons of essential witnesses is unacceptable and would have immediate and significant consequences," he added.

White House special counsel Ty Cobb told CNN in response to the speech that there is "no consideration" of firing Mueller.

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