Microsoft backs Icahn's bid to oust Yahoo board

Yang has been meeting with Yahoo's major stockholders during the past week, hoping to persuade them to give him a chance to prove the Sunnyvale-based company is worth more than the $33 per share that Microsoft previously offered.

Ballmer withdrew that bid after Yang sought $37 per share — a height the stock hasn't reached in 2 1/2 years.

In its Monday statement, Microsoft didn't mention how much it thinks Yahoo is worth now.

Industry analysts estimated Microsoft would likely pay anywhere from $28 to $33 per share if it takes another stab at swallowing Yahoo whole.

"Microsoft is still asking Yahoo shareholders to make a big decision with incomplete information," said Standard & Poor's Internet analyst Scott Kessler. "I could still see a scenario where the Yahoo board is replaced and Microsoft comes in with a bid that is lower than people want. Then what do you do?"

Microsoft more recently has been trying to pry away Yahoo's search engine for $1 billion, plus an additional $8 billion investment for a 16 percent stake in Yahoo's remaining operations.