Uber wants its former lead engineer to clear the air in the case involving Waymo.

The engineer at the crux of the Uber versus Waymo lawsuit has been given an ultimatum by his current employer — either deny stealing files from Alphabet's self-driving division or get out.

That's what Uber General Counsel Salle You wrote to Anthony Levandowski in a May 15 letter. Waymo, Levandowski's former employer, claims the engineer stole technical files before leaving the company and ultimately landing a job Uber.

"If you do not agree to comply with all of the requirements set forth herein, or if you fail to comply in a material manner, then Uber will take adverse employment action against you, which may include termination of your employment," Yoo wrote in the letter, according to Bloomberg.

Levandowski worked on Waymo's self-driving car before leaving to form his own autonomous startup, Otto. Uber eventually acquired Otto for $680 million and promoted Levandowski to head of its self-driving car operations.

Although Waymo has alleged that Levandowski stole thousands of files before departing the company, he isn't a defendant in Waymo's lawsuit.

Levandowski's lawyer argues that Yoo's demand is unconstitutional.

"Anything short of firing Mr. Levandowski to get him to waive his Fifth Amendment rights and attorney-client privileges would put Uber at risk of contempt, since it would fail to measure up to the Court's command that Uber exercise every lawful power it has over Mr. Levandowski," Miles Ehrlich, Levandowski's lawyer, said.

U.S. District Judge William Alsup, who's overseeing the case in the Northern District of California, has asked prosecutors to investigate the claim.