Microsoft’s Activision-Blizzard acquisition looks set to go sour within weeks. Just after the Redmond giant extended its proposed Call of Duty sharing deal with PlayStation for a decade, we’ve learned that The United States Federal Trade Commission (FTC) is considering filing an antitrust lawsuit to block the operation agreed between Microsoft and Activision-Blizzard..

It’s no secret that Microsoft’s Activision-Blizzard purchase deal hit Sony hard, and what’s more, since then, and quite possibly, the Japanese-born company has been maneuvering to prevent the transaction from being completed. On the other hand, the takeover of one giant by another giant is quite a temptation for antitrust agencies to get involved, which is what happened in this case.

An antitrust lawsuit against the Microsoft-Activision-Blizzard deal is not guaranteed, but the FTC appears to have done most of its research, which included statements from Microsoft CEO Satya Nadella and Activision-Blizzard CEO Bobby Kotick. If it deems it appropriate, the commission will submit the case to its own internal administrative court next month. Because the door is still open it is likely that the FTC will eventually give the operation a go-aheadbut while it arrives it is frozen and will not be completed until next year.

The prospect of the FTC filing an antitrust suit adds to a grim Phase 1 report from the CMA, the Competition and Markets Authority (CMA), which concluded at the time that Microsoft’s acquisition of Activision-Blizzard may lead to a “substantial lessening of competition in one or more markets in the UK.” Considering that CMA was once the frontrunner to knock off NVIDIA’s ARM purchase, it’s only logical to think that right now there’s a dark cloud hanging over the Microsoft/Activision-Blizzard deal.

Microsoft has already responded at CMA that its deal with Activision-Blizzard will not harm competitionbut the reality is, seeing the reaction of the stock markets, few people think it is true, and if not, the Redmond giant would not be trying to extend the Call of Duty sharing agreement with PlayStation.

As we’ve said before, it’s best to remain cautious, but it’s clear that things are getting uglier for Microsoft and Activision-Blizzard. If the FTC decides to file a lawsuit, it looks like both companies will have to present very good arguments and facts to get it through.