Oct. 28 (UPI) -- Former White House national security official Charles Kupperman did not appear in Congress Monday to testify as part of the impeachment proceedings against President Donald Trump, defying a subpoena.
Kupperman, former deputy to national security adviser John Bolton, had filed a lawsuit asking a judge to resolve the conflicting orders from the congressional subpoena compelling him to testify and the White House ordering not to cooperate. He could receive a contempt citation for failing to appear.
Kupperman's attorney Charles Cooper said his client wants the courts to resolve the matter before he appears.
"It is not Dr. Kupperman who contests your clients' constitutional claim," Cooper wrote in a letter to House intelligence committee Senior Investigative Counsel Daniel Noble. "It is President Trump and every president before him for at least the last half century, who have asserted testimonial immunity for their closest confidential advisers.
"If [the committee's] position on the merits of this issue are correct, it will prevail in court, and Dr. Kupperman, I assure you again, will comply with the court's judgment."
House investigators on the intelligence, foreign affairs and oversight committees have already deposed multiple witnesses in the inquiry, including U.S. Ambassador to Ukraine William Taylor.
The panels are trying to determine whether Trump withheld military aid to Ukraine for a Ukrainian investigation of Democratic presidential candidate Joe Biden and his son, Hunter. The White House has said the aid was withheld due to corruption concerns and Kiev would spend the money.
The impeachment inquiry is being led by Reps. Adam Schiff, Eliot Engel and Carolyn Maloney, who chair the intelligence, foreign affairs and oversight committees. They wrote in their lawsuit that efforts by the Trump administration to block witnesses is "an obvious and desperate tactic by the president to delay and obstruct the lawful constitutional functions of Congress and conceal evidence about his conduct from the impeachment inquiry."
Cooper said the suit wasn't discussed with anyone at the White House and Kupperman has no preference on the outcome of the investigation.
"It would not be appropriate for a private citizen like Dr. Kupperman to unilaterally resolve this momentous constitutional dispute between the two political branches of our government," Cooper said.
Investigators insisted Sunday that Kupperman comply with the subpoena.
"[He] has a simple choice to make: Either appear for a deposition [Monday] pursuant to a duly authorized subpoena, or abide by a baseless White House assertion that your client, a private citizen, should disregard his own legal obligations."
Kupperman was party to the July 25 phone call between Trump and Ukrainian President Volodymyr Zelensky.
"We had a very good conversation with the Ukrainian president. I had another conversation with him also, I think before that, which was the same thing," Trump said of the call Monday. "It was nothing."