Microsoft ( MSFT) will expand its advertising partnership with Facebook as part of a deal to take a $240 million equity stake in the social-networking site. The financial agreement, which allows Microsoft to sell international ads for Facebook, values the privately held site at $15 billion. The arrangement will also make Microsoft the exclusive third-party ad partner for Facebook. The news comes on the heels of speculation that Microsoft and Google ( GOOG) were both jostling to sell international ads for Facebook. Microsoft already had an existing arrangement to sell domestic ads for Facebook. "Making this investment and expanding this partnership will position Microsoft and Facebook to better take advantage of advertising opportunities around the world, and is a great win for not only for our two companies, but also our collective users and advertisers," Microsoft President of Platforms and Services Kevin Johnson said in a press release. Shares of Microsoft were off nearly 1% in after-hours trading to $30.96.