The two companies now have five working days to submit proposals to address its concerns, and if suitable suggestions are not submitted, the deal will be referred for a phase 2 investigation, allowing an independent panel of experts to examine the risks in greater detail.
At the same time, however, Spencer also confirmed that the Activision Blizzard games Overwatch, Diablo and Call of Duty would be on its Netflix-for-games subscription service Game Pass.
Both Microsoft and Sony are ploughing billions into filling out the catalogues of their subscription services.
The PlayStation owner has launched a competitor to Game Pass, PlayStation Plus Premium and spent $3.7bn on acquiring the Destiny developer, Bungie.
Microsoft has already bought ZeniMax, which makes the Skyrim, Fallout and Doom series, for $7.5bn.
The bidding war has funnelled cash to independent developers and publishers, but also raised fears of an inevitable bust to come once the boom times are over.
