As part of the inquiry, the UK Competition and Markets Authority (CMA) is soliciting public input on the matter until July 20. Based on the record, the CMA may then decide whether a more detailed investigation is warranted. The agency has a September deadline to make that decision, though the exact date could shift.

Microsoft has sought to anticipate regulatory scrutiny surrounding its deal, which it says would make the company the third-largest game publisher in the world after Tencent and Sony. (Sony announced in February it is buying the game studio Bungie for $3.6 billion, in another deal that adds to industry consolidation.)

Microsoft has embarked on a global charm offensive to preempt regulatory concerns. In February, it announced several commitments that will apply to its gaming business to head off any concerns that its position as a gatekeeper could give it anticompetitive leverage over game publishers or software developers, an allegation that has bedeviled Apple and Google around the world.

"It really behooves us to step forward quickly and proactively and be very transparent about how we will manage this business, with a clear eye toward the competition law issues and responsibilities that we have," Microsoft President Brad Smith told reporters at the time. Online Games