Xbox chief and Microsoft Gaming CEO Phil Spencer says Sony’s opposition to the Activision Blizzard deal comes down to the PlayStation maker wanting “to protect its dominance” in consoles. “The way they grow is by making Xbox smaller,” said Spencer in a recent Second Request podcast (Via Eurogamer).

Sony has been opposed to Microsoft’s $68.7 billion deal to acquire Activision Blizzard, and has focused on the future of Call of Duty in filings with regulators. “Sony is leading the dialogue around why the deal shouldn’t go through to protect its dominant position on console, so the thing they grab onto is Call of Duty,” says Spencer. “The largest console maker in the world raising an objection about the one franchise that we’ve said will continue to ship on the platform.”

Microsoft has reached a 10-year deal with Nintendo to make Call of Duty available on Nintendo consoles if the Activision Blizzard deal closes. That could potentially lead to Call of Duty releasing on Nintendo Switch for the first time.

Whether Call of Duty arrives on Nintendo consoles or Xbox Game Pass hangs in the balance right now, after the Federal Trade Commission (FTC) filed a legal challenge to try and block Microsoft’s plan to buy Activision Blizzard. Regulators in Europe are also closely examining the deal, with the EU on a March 23rd deadline to complete its in-depth investigation and issue a decision. The UK’s Competition and Markets Authority (CMA) is also performing a deeper review of the deal.