Carl Icahn, who is pressing for a board seat and changes at Motorola , has raised his stake of the struggling mobile phone maker's shares to 2.9% from 2.7%, according to a regulatory filing late on Monday.
The billionaire investor said in January he would seek a board seat to push the No. 2 maker of mobile phones into using some of its $11.3 billion cash pile to buy back more shares.
Icahn, who has agitated for change at many companies and is also seeking board seats at WCI Communities and Temple-Inland, has lobbied for shareholders to vote him to the board at Motorola's annual meeting on May 7.
Motorola, which has lost about a third of its market value, or $22 billion, in the last five months due to a sharp fall in phone prices and stiff competition, has urged shareholders not to support Icahn.