The Federal Trade Commission on Thursday sued to block Microsoft's planned $69 billion takeover of video game company Activision Blizzard, saying it could suppress competitors to Microsoft's Xbox game console and its growing games subscription business.

The FTC's challenge could be a test case for President Joe Biden's mandate to scrutinize big tech mergers. The commission voted 3-1 to issue the complaint after a closed-door meeting, with the three Democratic commissioners voting in favor and the sole Republican voting against.

The complaint points to Microsoft's previous game acquisitions, es...