UPDATE 1-VivendiGÇÖs chairman loses battle for Ubisoft

(Recasts, adds detail and Ubisoft comment)

PARIS, March 20 (Reuters) - Vivendi Chairman Vincent Bollore has lost a two-year battle against the founders of Ubisoft, with his French media group announcing plans to sell its stake in the video games maker for 2 billion euros ($2.45 billion).

The move represents a strategic setback for Vivendi, which has pledged to make video gaming one of its key pillars along with advertising, music and pay-TV.

Vivendi, which had been raising its holding in Ubisoft said it would sell its 27.3 percent stake in the company best known for its Assassin's Creed and South Park games.

The stake-building by Vivendi since 2015 had prompted Ubisoft's founding Guillemot family to court Canadian investors to fend off any hostile approach.

After the sale Vivendi will remain active in video gaming through its acquisition of mobile game maker Gameloft, which was also founded by a Guillemot brother but is much smaller than Ubisoft, the French leader in this market.

Vivendi's exit, however, is a setback for Bollore amid growing concerns about other ventures in Italy.

Ubisoft told journalists during a call on Tuesday that Vivendi had approached it several weeks ago about its intention eventually to sell its stake. Ubisoft started tapping up potential investors at that stage.

The Vivendi sale brings Ubisoft two new long-term investors, the Relationship Investing arm of Ontario Teachers' Public Equities division and Chinese social network and gaming company Tencent. The deal also includes a share buyback by Ubisoft, a share purchase by Guillemot Brothers SE and an accelerated bookbuilding with institutional investors.

As part of the transaction, Ubisoft and Tencent have also announced a partnership that will speed the reach of Ubisoft franchises in China in the coming years. ($1 = 0.8159 euros) (Reporting by Maya Nikolaeva and Matthieu Rosemain Editing by Jane Merriman and David Goodman)