U.S. antitrust regulators have asked a California federal court to put a temporary block on Microsoft’s (NASDAQ:MSFT) $69 billion purchase of Activision Blizzard (NASDAQ:ATVI), potentially placing a fresh legal hurdle before the gaming industry’s biggest ever deal.

The Federal Trade Commission is already set to carry out its own legal proceedings beginning in August. The FTC is now requesting that the court prevent the deal from being completed until a decision, in this case, is made.

The FTC argued that the tie-up, which would see Microsoft take control of the maker of the popular video game title Call of Duty, would give the tech giant the “ability and increased incentive to withhold or degrade Activision’s content in ways that substantially lessen competition.”

Meanwhile, Microsoft’s president and vice-chair, Brad Smith, has said that he “welcomes” the chance to defend the merger in a federal court.