Gary Forsee, chief executive of Sprint Nextel, appears to be on his way out as the company's board of directors has launched a recruiting effort to find an experienced telecom executive to replace him. Forsee's big bet on the as-yet-unproved WiMax wireless technology may be a key reason.

The news that Sprint's board wants to find a new chief executive, first reported by the Wall Street Journal, also caused damage Friday to Sprint's WiMax partner, Clearwire Corp., whose stock plunged more than 13% in early trading. Citing Sprint's WiMax investments and other challenges, investment analysts lowered their ratings on Clearwire.

Forsee has been beset by a myriad of problems including a drop in cell phone subscribers, a drop in the company' stock price, high prices it pays to AT&T and Verizon to access their fiber-optic networks, and difficulties in melding Nextel into the Sprint company framework in the wake of the merger of the two firms in 2005.

But the $5 billion bet Sprint is placing on WiMax has caught in the craws of investors, particularly in those of financier Ralph Whitworth of Relational Investors LLC. Citing concerns over Sprint's planned deployment of WiMax, Whitworth this week called on Sprint's board of directors to "immediately" deal with Forsee and the leadership of the company. As it turned out, the board was already dealing with the situation and has been interviewing replacement candidates, according to the Journal.

"We do not have any comment on the recent reports regarding Gary Forsee," said Sprint spokesman James Fisher in an e-mail Friday. He added that the firm is "moving ahead" with the WiMax plans the company outlined in August at its technology summit.

At that time, Sprint said it would initiate a "soft launch" of WiMax by the end of 2007 in the Chicago and Washington/Baltimore markets.

WiMax, a wireless technology that promises faster speeds and greater range than Wi-Fi, could be huge " if it works as planned. But it has been slow to roll out and, in fact, the WiMax Forum still hasn't approved a workable standard; equipment providers are proceeding with WiMax gear manufacturing and deliveries, promising service providers that WiMax can be easily upgraded via software updates when a formal standard is approval.

As a stopgap to high-speed WiMax, Sprint has been rolling out CDMA2000 EV-DO Rev A, another advanced high-speed mobile wireless service. The challenge of melding the two advanced technologies -- EV-DO and WiMax -- and also dealing with Nextel's spectrum legacy has been confusing to many consumers.

Forsee forged a WiMax alliance with Clearwire in July and the two firms agreed to give their respective customers roaming rights to each other's networks. Clearwire chairman Craig McCaw, the cellular pioneer who successfully built different consumer wireless firms, appeared to be following a similar playbook to the one he used in the early days of Nextel -- gradually accumulating spectrum licenses from original holders. But Clearwire has found that collecting the licenses for WiMax has been difficult.

At its technology summit meeting, Sprint said it expected its WiMax services to cover 124 million people by 2010 but, now many investors appear to be reluctant to wait that long.