NEW YORK -- Carl Icahn has launched a proxy battle to force Yahoo Inc to reopen buyout talks with Microsoft Corp, the billionaire investor said in a letter to the Internet company on Thursday.

Icahn has formed a 10-member rival slate for Yahoo's board to push the company to accept Microsoft's bid of $33 per share, or $47.5 billion.

He also disclosed in the letter to Yahoo Chairman Roy Bostock that he had acquired 59 million shares and had sought antitrust clearance from the U.S. Federal Trade Commission to acquire up to about $2.5 billion worth of Yahoo Stock.

"It is clear to me that the board of directors of Yahoo has acted irrationally and lost the faith of shareholders and Microsoft," Icahn wrote.

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