San Francisco ? The battle for Yahoo Inc. heated up over the weekend when the Internet giant rejected a proposal from Microsoft Corp. and billionaire investor Carl Icahn to break up Yahoo.

The “take it or leave it” proposal entailed selling Yahoo’s search business to Microsoft and handing control of the rest of the company to Icahn, Yahoo Chairman Roy Bostock said in an interview.

It was also conditioned on the removal of Yahoo’s board and management.

In a deal presented to Yahoo on Friday, Microsoft Chief Executive Steve Ballmer gave Yahoo’s board 18 to 24 hours to consider the terms that were essentially non-negotiable, Bostock said.

Yahoo’s counterproposals to sell Yahoo to Microsoft for $33 a share or to negotiate a better deal for its search business at a later date were rebuffed, Bostock said. He characterized Microsoft’s behavior throughout the takeover saga as “erratic and unpredictable” and accused Microsoft of engaging in bullying tactics.

“This latest iteration is trying to bludgeon the Yahoo board into a deal,” Bostock said.

Icahn could not be reached for comment. A Microsoft spokesman declined to comment.