STORY: Microsoft's $69 billion deal for "Call of Duty" maker Activision Blizzard has hit a big hurdle.
Britain's antitrust watchdog said Thursday (September 15) it would hold an in-depth probe into the move.
It comes after the tech giant failed to offer assurances about competition concerns.
The deal was announced in January this year.
It needs approval in the United States and other major areas like the EU and China.
Britain's Competition and Markets Authority raised concerns earlier this month.
It said the takeover of the video game publisher could hurt competition in gaming consoles, subscription services and cloud gaming.
That if Microsoft did not give competitors access to Activision's best-selling games.
A source told Reuters that Microsoft would pay a $3 billion break-up fee if the deal fell through.
That would suggest the company was confident of winning antitrust approval.