The 3-year-old partnership between Microsoft and Facebook that has become an important weapon against archenemy Google started with an offer to buy what now has become the world's largest online social network, a Microsoft executive has confirmed.

Fritz Lanman, senior director of corporate strategy and acquisitions at Microsoft, confirmed Friday that Microsoft Chief Executive Steve Ballmer offered to buy Facebook during a meeting with its founder and CEO Mark Zuckerberg, TechCrunch reported.

"Yeah, we tried to acquire Facebook," Lanman said during an on-stage interview at the Le Web conference in Paris. "Facebook had a lot of similarities to Microsoft back in the day."

The acknowledgement as reported by TechCrunch doesn't have Lanman confirming that Microsoft was willing to pay $15 billion for Facebook, which was reported in the book "The Facebook Effect" by David Kirkpatrick. Asked whether that was the amount offered, a Microsoft spokesman replied, "No comment."

"They're going to let his words speak for themselves," the spokesman said of Microsoft.

Kirkpatrick claimed that $15 billion is what Ballmer offered Zuckerberg during their meeting in Palo Alto, Calif., where Facebook has its headquarters. When Zuckerberg refused to sell, Microsoft did what it believed was the next best thing, an investment of $240 million in Facebook that was announced publicly in October 2007. Based on the investment, Facebook's valuation at the time was $15 billion.

Since 2007, Microsoft and Facebook have worked together building several fronts against Google. In July 2008, Microsoft reached a deal with Facebook to provide Web search services to users of the social network. Since then, Microsoft has expanded its search capabilities to include publicly posted information on Facebook and Twitter.

This year, Microsoft launched Docs for Facebook, which lets members of the social network create and share Microsoft Office documents. The service is seen as a way to steer Facebook users away from Google Docs to Microsoft's online document sharing and collaboration service.

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