NEW YORK – Activist investor Carl Icahn said Monday that replacing Yahoo Inc.'s current board of directors would ensure an acquisition deal with Microsoft Corp.

In urging shareholders to vote for his slate of nine directors, Icahn said he was confident the new board would “in very short order” present shareholders with an offer to sell the whole company or its search functions with large financial guarantees.

Icahn made a filing with the Securities and Exchange Commission Monday after Yahoo revealed late Saturday that it had spurned Microsoft's latest attempt to buy its online search engine in a joint proposal made with Icahn.

Icahn, who has no experience running an Internet company, would have been left in charge of Yahoo's remaining pieces had an agreement to sell the search engine to Microsoft been reached.

“During the next few weeks you will be hearing from us about how these changes can be effectuated and a transaction structured to enhance value for all shareholders,” Icahn said in a letter to shareholders filed with the SEC.

Microsoft first offered to buy Yahoo five months ago, but the software maker ultimately walked away from a deal in May after last-ditch efforts to negotiate a mutually acceptable sale price failed. Icahn started a shareholder rebellion a few weeks later.

Hoping to fend off the revolt, Yahoo's board is now willing to sell the entire company to Microsoft for $47.5 billion, or $33 per share – a price it rejected as too low 10 weeks ago. But Microsoft has said it has no interest in buying Yahoo in its entirety as long as the company's current board is in place.

Icahn said in his filing that he received assurances from Microsoft CEO Steve Ballmer that Microsoft “would be willing to enter into discussions regarding a transaction immediately” if Icahn's slate is elected in an Aug. 1 vote.

Yahoo shares finished Friday at $23.57, after rising 10 percent last week on hopes that Microsoft's decision to side with Icahn might pave the way for a deal.

Microsoft's latest run at Yahoo indicates that the world's largest software company still believes it needs its rival's search engine to counter the intensifying threat posed by Google Inc.'s dominance of the Internet advertising market.

Yahoo shares fell 92 cents, or 3.9 percent, to $22.65 in morning trading, while Microsoft stock added 51 cents, or 2 percent, to $25.76.