Xbox v PlayStation: Giants clash over Call of Duty
Xbox owner Microsoft has hit back at claims its plan to buy the maker of Call of Duty may unfairly affect its rivals, including Sony, which owns PlayStation.
Microsoft wants to buy Activision Blizzard, which also makes Overwatch and Candy Crush, for $68.7bn (£59.2bn).
UK watchdog looking into the plan has said Microsoft could use Activision games to "out-compete" its rivals.
Microsoft said it still hoped the deal would be closed by June 2023.
Competition regulators in Saudi Arabia and Brazil have already approved it. 
But last month, the Competition and Markets Authority announced it would be asking an independent panel to look into the proposal.
Activision Blizzard is one of the world's largest video game developers and publishers, and the Call of Duty franchise has attracted millions of players.
And the CMA suggested buying it could allow Microsoft to monopolise top games such as Call of Duty by making them available primarily on Xbox consoles, PCs and Game Pass, its cloud gaming service.
In a detailed account of its decision to launch an in-depth investigation, published today, the CMA says that "Call of Duty is sufficiently important that losing access to it (or losing access on competitive terms) could significantly impact Sony's revenues and user base". 
It also said that "Microsoft has followed this approach in several past acquisitions of gaming studios, where it made future game releases from those studios exclusive in consoles to Xbox".
Microsoft says it is committed to keeping Activision's existing titles, including Call of Duty, available on the PlayStation. 
But future titles could be treated differently. 
Microsoft already owns 23 games makers, including Minecraft maker Mojang, and Fallout and Skyrim creator Bethesda. 
Bethesda's upcoming Starfield game will now be an Xbox and PC exclusive, and the CMA suggested that this could also be the case for the studio's Elder Scrolls VI,  based on Microsoft's public statements.
Microsoft says:
And, In a report seen by BBC News, Microsoft calls the CMA's concerns "a novel theory of harm, unsupported by precedent, economic literature or the evidence".
In a statement, Sony said the firm believes the deal is "bad for competition, bad for the gaming industry and bad for gamers themselves.
"This deal would give Microsoft's Xbox ecosystem a unique combination of tech and content, and hence a dominant position in gaming, with devastating consequences for consumers,  independent developers, and Sony itself," it added.
Follow Zoe Kleinman on Twitter @zsk