The billionaire investor sets the stage for a proxy fight and possible sale of Motorola's handset unit.
Motorola's management and billionaire investor Carl Icahn are heading for another showdown.
In a March 5 filing with the Securities and Exchange Commission, Icahn, already Motorola's largest stakeholder, disclosed that he had raised his stake in the company to 6.3 percent. In all, Icahn or Icahn-controlled entities own 142 million shares of Motorola.
Icahn has said Motorola would be better off by selling its struggling mobile phone division and is pushing for four new board members who are friendly to his interests. Icahn last year failed to gain a seat on the Motorola board.
According to a separate March 5 SEC filing, Motorola urged shareholders to reject Icahn's bid for control of the board.
"The Board urges you not to vote any proxy sent to you by the Ichan affiliates," the filing stated. "If you have previously voted a proxy sent to you by the Icahn affiliates, you can revoke it by submitting a timely, later-dated proxy."
Motorola, the nation's third-largest cell phone maker, announced in January another sharp decline in mobile handset sales, resulting in an 84 percent drop in fourth-quarter net income. The company said it shipped 40.9 million handset units in the fourth quarter, a dramatic drop from the 65.7 million units shipped a year ago.
Motorola's mobile devices division represents about half of the company's sales. After introducing the successful RAZR model in 2004, Motorola has struggled to launch another hit cell phone, driving it from the No. 2 spot among dominant handset makers. Nokia and Samsung are now the top two handset manufacturers.