House Deputy General Counsel Todd Tatelman said the House viewed the suit as an effort to stall the impeachment process.

“We believe strongly that this case serves no other purpose than to delay,” Tatelman said. “The House believes its subpoena is complete valid. It is 100 percent enforceable.”

Justice Department attorney Elizabeth Shapiro said she saw no urgency that required accelerating the case. “We don’t think there’s a real emergency or need,” she said.

House leaders have not set a formal timetable for the impeachment process, but many Democrats want to see the House’s part of the process completed before year’s end..

Tatelman said he was ready to file a motion by Tuesday to dismiss the case on the grounds that the suit was improper because of the Constitution’s provision creating immunity for activities involving congressional debate.

However, Leon gave the House a full two weeks to do so and said Kupperman’s lawyers would not need to respond until the day before Thanksgiving.

“These are very important and challenging issues that have to be wrestled with,” Leon said.

Kupperman’s attorney Charles Cooper stressed that his client wasn’t taking a position on whether the subpoena is or is not valid, but simply wanted the court to tell him whether to side with the president or the House subpoena.

“We have no dog in the merits fight, Your Honor,” Cooper said. “Dr. Kupperman is basically in a classic Catch-22 here. … Dr. Kupperman is indifferent to the outcome.”

After Leon raised the issue, Cooper acknowledged that Kupperman’s onetime boss, former national security adviser John Bolton, could also join the case. Bolton has declined to appear voluntarily and is also facing the possibility of a subpoena. Cooper said adding any of his other clients to the case would not cause any delay.

House lawmakers want to talk to Bolton and Kupperman about allegations that Trump sought to use U.S. aid to Ukraine in order to coerce leaders there into announcing an investigation that could be politically damaging to one of Trump’s potential opponents in next fall’s election, former Vice President Joe Biden.

After the roughly 40-minute hearing Thursday, it was not even clear whether a ruling Leon would issue following the House motion would definitively resolve Kupperman’s duty to testify, or would simply address the threshold issue of whether he has the right to pursue his unusual suit asking the court to resolve the competing claims of two branches of government.

Leon, an appointee of President George W. Bush, held the session on Thursday despite a request from lawyers for the House and the Justice Department to delay it because of a simultaneous hearing nearby on a similar suit the House filed against former White House counsel Don McGahn after he ignored a subpoena at Trump’s request.

When Shapiro rose near the end of the hearing to ask Leon to adjust a date because of the Thanksgiving holiday, Leon lit into her.

“You’re obviously not familiar with this court,” Leon said to Shapiro, a Justice Department veteran who has appeared in Leon’s courtroom on scores of occasions over the past two decades. “When we’re talking about a matter of this consequence to this country, you roll your sleeves up and get the job done. … If you can’t do it, you have colleagues who can.”