Uber has asserted attorney-client privilege to prevent Waymo from reviewing an internal due-diligence report related to the Otto acquisition.

Uber may have been dealt another blow in the legal battle with Waymo as a magistrate judge apparently shoots down its assertion of attorney-client privilege for an important document.

The lawsuit centers around Uber's acquisition of Otto, a startup formed by Google's former head of self-driving car engineering, Anthony Levandowski, after he left the search giant. Waymo has argued that Otto was created as part of a conspiracy to steal trade secrets from Google without directly exposing Uber to legal liability.

Potential risks of Otto acquisition were likely discussed in due-diligence documents that Waymo has requested in the lawsuit. Uber claimed the document was protected by attorney-client privilege because it involved discussions with internal lawyers.

The disagreement was left to a magistrate judge to establish a ruling under seal, however the US federal judge overseeing the primary lawsuit apparently revealed the outcome in court.

"Are you appealing the ruling against you on the due diligence report?" US District Judge William Alsup asked Uber's lawyers in a San Francisco courtroom, as quoted by Reuters.

Levandowski was fired recently for failing to comply with Uber's internal investigation and asserting his Fifth Amendment right to avoid testifying in the case. He was not listed as a defendant in the case, which focuses instead on Uber's knowledge of his alleged actions.

The document could reveal what Uber's executives knew, if anything, about Levandowski's actions and intentions related to his departure from Google and Otto's acquisition.