In a letter Saturday to attorneys representing Charles Kupperman, the president’s former deputy national security adviser, leaders of three House committees said his lawsuit is “lacking in legal merit and apparently coordinated with the White House,” and failure to appear for his deposition “will constitute evidence that may be used against him in a contempt proceeding.”

“Such willful defiance of a duly authorized subpoena may cause the committees to draw an adverse inference against the president,” the letter said. “The White House’s overbroad assertion of ‘absolute immunity,’ at its core, is another example of the president’s stonewalling of Congress and concerted efforts to obstruct the House’s impeachment inquiry.”…

Kupperman on Friday made the argument that he was caught between two different directives and asked a federal judge whether he must appear. He said in court papers that he faces “irreconcilable commands” — a subpoena from House Democrats requiring him to cooperate and an order from the White House not to testify.