Charles Kupperman, the deputy to former national security adviser John Bolton, was scheduled to appear before the joint committees carrying out the impeachment inquiry, but according to his attorney, he will not be testifying Monday.

Kupperman, who was subpoenaed by committees, has also been told by the White House that he could not appear before the committees. Torn between the legislative and executive branch directives, Kupperman filed a lawsuit last week in the U.S. District Court for the District of Columbia requesting that the court decide for him whether he "should comply with the House's subpoena or with the President's assertion of immunity and instruction that he not appear and testify," Kupperman's attorney, Charles Kupperman said in a statement last week.

According to his attorney, Kupperman took "no position" on whether Congress or the White House should prevail. He only wanted to do whatever the judicial branch deemed to be the lawful and binding course of action.

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Absent a ruling, Kupperman's attorney said he would not appear — unless the court issues a ruling instructing him to appear.

Kupperman was on the July 25 call between President Trump and Ukrainian President Volodymyr Zelensky, The Wall Street Journal reported.

Bolton, too, has not ruled out appearing before Congress. Attorneys for the former national security adviser are consulting with lawmakers about possibly cooperating with the impeachment inquiry, CBS News' Paula Reid reported last week.

Reporting by Margaret Brennan.