US regulators have filed a complaint aimed at stopping Microsoft’s planned $69bn (£50bn) takeover of Call of Duty games maker Activision Blizzard.
Microsoft, which owns Xbox, said in January that it had agreed an all-cash deal – the biggest in the gaming sector to date.
But regulators globally, including in the UK, have taken great interest since.
The UK’s Competition and Markets Authority said in September the deal could restrict competitors’ access to Activision Blizzard games and limit competition in the emerging cloud gaming market.
On Thursday, the US Federal Trade Commission (FTC) said it was bidding to block the deal on the grounds that rivals would have restricted access to gaming content.
The agency said that Microsoft had a record of buying valuable gaming content and using it to suppress competition from rival consoles.
Holly Vedova, director of the FTC’s Bureau of Competition said: “Microsoft has already shown that it can and will withhold content from its gaming rivals.
“Today we seek to stop Microsoft from gaining control over a leading independent game studio and using it to harm competition in multiple dynamic and fast-growing gaming markets.”
The US tech giant has made several attempts to allay regulators’ fears including a commitment to to bring Call of Duty to Nintendo platforms for the first time. It has made the same 10-year promise to Sony.
Microsoft president Brad Smith responded to the FTC’s complaint: “While we believed in giving peace a chance, we have complete confidence in our case and welcome the opportunity to present our case in court.”