Updated Thursday 1:00 AM PDT with further details of Icahn's past proxy efforts.
Billionaire investor Carl Icahn is planning to wage a proxy fight against Yahoo, in a move that could ultimately kick out Yahoo's entire board, according to a Reuters report.
Icahn has received commitments from at least 12 potential board members to run for some or all of Yahoo's 10 board seats, which are all up for re-election at the company's July 3 annual shareholders meeting, according to Reuters.
Icahn was expected to unveil his plans as early as Wednesday night, according to the report. The deadline for Yahoo or any shareholder to name a slate is by the end of the day Thursday.
Shares of Yahoo on Wednesday closed up 2 percent to $27.14 a share, spurred by expectations Icahn would move forward on a proxy fight, potentially paving the way for a sale of the Internet search pioneer.
Less than two weeks ago, Microsoft withdrew its sweetened cash-stock offer for Yahoo, valued at $33 a share, after a three-month period in which its initial offer of $31 a share remained virtually comatose.
After Microsoft withdrew its offer on May 3, Yahoo's stock took a hammering during the next trading day and has since bounced between a low of $24.20 to as high as $27.36 per share during intraday trading on Wednesday.
Prior to Microsoft's $31 offer, Yahoo's stock was trading around $19 a share.
Microsoft and Yahoo declined to comment on reports of Icahn's proxy plans.
He's had mixed results on those companies when he's made a run for them through some sort of shareholder activist campaign.
At both biotech company ImClone Systems and video rental giant Blockbuster, Icahn was able to gain a board seat, but ImClone continues to post losses and Blockbuster shares have lost nearly half their value since the fall.
Nonetheless, Icahn and the video rental giant have managed to persuade a reluctant electronics retailer Circuit City Stores to contemplate an acquisition. Earlier this month, Circuit City Stores agreed to open its financial books for Icahn to take a peek, after the shareholder activist said he would consider buying the electronics chain if Blockbuster's offer fell through.
Folks who are familiar with Icahn's efforts at these companies and others, where he has tried to gain board seats, acknowledge he comes with detailed ideas, versus vague suggestions on how to improve the operations of the companies.
As the campaign to win the hearts and minds of Yahoo investors kicks in, don't be surprised to watch a knock-down, drag-out fight between the two parties. Proxy solicitors note that proxy fights are often like watching a presidential campaign.
Some are already gearing up for the fight, such as Jim Safka, chief executive of Yahoo rival Ask.com.
"I love it," said Safka, whose company announced Wednesday plans to buy Lexico Publishing Group said. "Just when you thought Microsoft and Yahoo were going to get on with their lives, it's going to paralyze them once again."
( CNET News.com Stephen Shankland and Ina Fried contributed)