Wireless carrier Sprint Nextel Corp. (S) said Monday that Chief Executive Gary Forsee is stepping down and that its board is looking for a replacement, amid concerns over customer defections and calls for a new leader.

The board believed that it was time to "put in place new leadership to move the company forward in improving its performance" and will focus its search on candidates outside the company, Sprint said.

Chief Financial Officer Paul Saleh will serve as acting CEO until a permanent replacement is named, it said.

The company also lowered its operating revenue forecast for 2007.