Sprint Nextel Corp. Chief Executive Officer Gary Forsee stepped down after failing to wrest customers from Verizon Wireless and AT&T Inc.

Forsee will leave immediately, Sprint said today in a Business Wire statement. The company, the third-largest U.S. wireless carrier, has started a search for his replacement.

After two years trying to make the $36 billion purchase of Nextel Communications Inc. work, Forsee lost investor support as about 700,000 monthly contract customers fled in the past year.