The former deputy to ex-White House official John Bolton wants clearance from a court before he testifies in the impeachment inquiry into President Donald Trump’s dealings with Ukraine, according to a report.

Charles M. Kupperman, who served as deputy national security adviser to the Trump administration, filed a lawsuit Friday asking the court to determine whether he can serve as a witness, the New York Times reported.

Kupperman claims White House lawyers told him not to appear for his scheduled testimony on Monday, and he’s uncertain whether to follow the president’s orders or the subpoena from House Democrats seeking his appearance.

“It is not possible for Plaintiff to satisfy the commands of both the House Defendants on the one hand, and President Trump on the other,” the suit says.

Kupperman’s lawyer, Charles Cooper, also represents Bolton. Democrats consider both to be key witnesses in the impeachment inquiry.

Trump said he fired Bolton as national security adviser on Sept. 10, the day before the president released the $391 million aid to Ukraine that the impeachment investigation centers on. Bolton claims he resigned. Kupperman replaced him as acting national security adviser and stepped down several weeks later.

The lawsuit indicates Cooper could also fight for Bolton to testify.