The Justice Department and the House have asked a federal judge to postpone the court hearing Thursday about impeachment witness Charles Kupperman's testimony.
The judge, Richard Leon of the US District Court in Washington, has not yet responded.
Thursday has been shaping up to be one of the most consequential days in court so far for the House impeachment inquiry and the White House's attempts to stonewall. Two hearings are scheduled that will test the White House's claim that its staffers are immune from testifying.
Leon had scheduled the hearing after Kupperman, a former deputy national security adviser, asked the court whether he needed to testify. The House has subpoenaed Kupperman but the White House had blocked him from testifying on Monday, claiming absolute immunity for White House officials in the impeachment probe.
The House and Justice Department agreed to seek the postponement, according to their filing Tuesday, because another court hearing they must attend is happening the same afternoon before a different judge. That case is about immunity from congressional testimony for another White House staffer, former White House counsel Don McGahn, as the House seeks his testimony in its impeachment probe.
Both sides have asked Leon to reschedule the Kupperman court hearing before November 6. Leon had originally scheduled to meet with lawyers for the Trump White House, the House of Representatives and Kupperman on Thursday "due to the time-sensitive nature of the issues raised in this case."
Kupperman, who served until last month as deputy national security adviser at the White House, was listening in on the July 25 phone call when, according to a White House transcript, Trump pressed Ukrainian President Volodymyr Zelensky to investigate former Vice President Joe Biden.
Kupperman's lawsuit raises additional questions about possible testimony from former national security adviser John Bolton, as Kupperman's lawyer Charles Cooper also represents Bolton.
"Plaintiff is faced with irreconcilable commands by the Legislative and Executive Branches of the Government and, accordingly, seeks a declaratory judgment from this Court as to whether he is lawfully obliged to comply with a subpoena issued by the House Defendants demanding his testimony '(p)ursuant to the House of Representatives' impeachment inquiry,' or he is lawfully obliged to abide by the assertion of immunity from congressional process made by the President in connection with the testimony sought from Plaintiff," the lawsuit states.
Kupperman's lawsuit includes a copy of a letter that White House counsel Pat Cipollone sent to Cooper directing Kupperman not to comply with the subpoena and maintaining that he would be protected by "constitutional immunity."