A federal judge on Thursday fast-tracked a case involving a key impeachment witness caught between House Democrats seeking to compel his testimony and a White House order to defy a congressional subpoena.

Judge Richard Leon, a George W. Bush appointee to the Federal District Court in D.C., called the legal dispute over the testimony of Charles Kupperman, a former deputy to former National Security Advisor John Bolton, a “matter of great public interest and a matter of great urgency for the country.”

Kupperman was on the July 25 phone call between President Trump and Ukrainian President Volodymyr Zelensky that is at the center of the impeachment inquiry.

The judge set a Dec. 10 date for oral arguments.