UPDATE 1-Motorola's former mobile chief Reed leaves

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SAN FRANCISCO, March 7 (Reuters) - Motorola Inc (MOT.N), the third-biggest mobile phone maker, said on Friday that Stu Reed, the former president of its struggling cell phone unit, is leaving the company, effective immediately.

Reed's departure, the latest in a series of executive reshuffles at Motorola, comes a month after Chief Executive Greg Brown took over the unit and said he was considering options such as splitting it off from the rest of the company.

Motorola's mobile unit has been losing money for the last year, when it ceded its No. 2 global ranking to Samsung Electronics (005930.KS) as demand for its phones weakened. Motorola has been punished for failing to come up with a strong successor to the once-lauded Razr phone.

It said last week that it was looking for a full-time manager for the phone unit, which Brown has said consumes about 80 percent of his time.

Some analysts have said it could be difficult for the company to attract top candidates to the job. Brown has warned that the unit faces a challenging 2008.

For the second year in a row, Motorola is also facing a proxy battle with activist investor Carl Icahn, a 6.3 percent shareholder who is looking to put a slate of four directors on the board. Icahn failed to win a board seat last year.

Reed had headed the cell phone unit since the summer of 2007. In his previous role as supply chain manager, Reed helped save money for Motorola by consolidating suppliers, the company said. (Reporting by Scott Hillis in San Francisco and Sinead Carew in New York; Editing by Gary Hill)