Sprint Nextel Executive Chairman Tim Donahue will retire effective Dec. 31, and former Liberty Media President and CEO Robert Bennett has been appointed to the Sprint Nextel board, the wireless carrier announced today.

Donahue was CEO of Nextel Communications before engineering a merger with Sprint last year, when he became executive chairman of the new company. Donahue reportedly had agreed to remain in that position through 2008, but his resignation will be effective two years prior to that schedule.

"I have poured my heart and soul into Sprint Nextel and I am confident that the promise of the merger will be realized," Donahue said in a prepared statement. "Instead of being in the thick of the action, it's time for me to start cheering Sprint Nextel along from the sidelines.”

Although Sprint and Nextel officials hailed the $36 billion deal as a “merger of equals,” most industry observers acknowledged it as a Sprint buyout of Nextel. As a result, Donahue’s early resignation was not entirely unexpected, said Ovum wireless analyst Roger Entner.

“For anybody who was at the press conference when Sprint was launched at the New York Stock Exchange, this doesn’t come as a surprise at all,” he said. “If you looked at [Sprint CEO] Gary Forsee, he looked like he was in charge. Tim Donahue looked checked out.”

Donahue did “a fantastic job” at Nextel but played a limited role in the combined company, so his departure will not have “any impact whatsoever” on Sprint Nextel, Entner said.

“You can’t give [Donahue] enough credit for what happened at Nextel,” he said. “I don’t think you can give him much credit for what’s happened at Sprint Nextel in the last year or so.”

Sprint Nextel’s board will announce a new chairman later, but Robert “Dob” Bennett will join the board immediately, the company said. After serving as president and CEO of Liberty Media from April 1997 to August 2005, Bennett currently is president of the Discovery Holding Company, which was spun off from Liberty Media last year.

Sprint Nextel will benefit from Dob's expertise in the communications and entertainment sector as well as his strong financial experience," Forsee said in a prepared statement. "Dob is extremely focused and will bring tremendous industry knowledge and financial acumen to Sprint Nextel. We are pleased to have him join the board."