The US Federal Trade Commission said Thursday it has officially dismissed its complaint challenging Microsoft's (MSFT) acquisition of Activision Blizzard, following a failed bid to block the deal in federal court.

The agency cited a May 7 ruling by the Ninth Circuit, which upheld a lower court's decision denying the FTC's request for a preliminary injunction against the transaction.

The FTC said it determined that continuing administrative litigation would not serve the public interest.

The dismissal effectively ends the Commission's efforts to unwind Microsoft's $69 billion acquisition of the game publisher behind Call of Duty and World of Warcraft, it said.

The case is now closed, with no further action expected from the agency, the FTC said.

Microsoft and Activision Blizzard did not immediately respond to MT Newswires' request for comment.