UPDATE 1-Sprint promises WiMax rollout, no mention of JV

(Adds Sprint on WiMax, analyst comment, other details)

By Sinead Carew

LAS VEGAS, April 1 (Reuters) - Sprint Nextel Corp (S.N: Quote, Profile, Research) disappointed investors on Tuesday by failing to announce a joint venture with cable companies to offer WiMax services, but said it would proceed with its plan to roll out a next-generation high-speed wireless network.

Sources familiar with the matter told Reuters last week that Sprint and Clearwire Corp (CLWR.O: Quote, Profile, Research) were in talks to combine their WiMax assets in a venture with funding from Comcast Corp (CMCSA.O: Quote, Profile, Research), Time Warner Cable Inc (TWC.N: Quote, Profile, Research), Intel Corp (INTC.O: Quote, Profile, Research) and Google Inc (GOOG.O: Quote, Profile, Research).

Investors had expected Sprint Chief Executive Dan Hesse to use a keynote speech at the CTIA mobile convention Tuesday to announce the venture. But he made no mention of any talks and did not say when the first WiMax markets would launch.

Sprint shares rose 7.5 percent before Hesse's speech but ended the day down 0.15 percent at $6.68 on the New York Stock Exchange.

Hesse showed videos describing WiMax, which promises network speeds five times faster than today's wireless Web links. Hesse said WiMax would support popular services such as mobile social networking and media downloads.

"We will be able to offer a form of visual social network ... a form of YouTube on steroids," the CEO said.

Sprint, criticized for a plan to spend $5 billion on WiMax by 2010, has said it was in talks with Clearwire on roaming agreements. Both have said separately they were looking for outside funding for WiMax.