Sprint seen unveiling a HTC WiMax phone at CTIA

* Sprint seen unveiling HTC Supersonic WiMax phone at CTIA

* Sprint shares close up 4.6 percent on NYSE

NEW YORK, March 17 (Reuters) - Sprint Nextel (S.N) will unveil a cellphone from HTC Corp (2498.TW) next week that will be the first to support WiMax, Sprint's fastest wireless service, according to analysts.

Sprint, the No. 3 U.S. mobile service struggling to stop customer losses, is expected to show the device at its press event on March 23 during the annual CTIA industry trade show.

At the same wireless telecommunications industry show, No. 2 U.S. mobile service AT&T Inc (T.N) is expected to announce which Palm Inc PALM.O phones it will support, according to at least one analyst. AT&T said in January that it would have new Palm phones in the first half of this year.

Sprint had promised it would have a WiMax phone on the market later this year, but it has not announced a specific launch date. It declined comment for this story as did HTC.

The HTC phone would support Sprint's CDMA network, according to one analyst, and the higher speed WiMax network operated by Clearwire Corp (CLWR.O), in which Sprint has a roughly 56 percent ownership stake.

"Our checks indicate that Sprint will launch a CDMA/WiMax handset at CTIA called the HTC Supersonic," Macquarie analyst Philip Cusick said in a research note.

Another analyst, Avi Greengart from Current Analysis, also said he expects the device announcement at the show.

"Sprint is going to announce their device plans for WiMax," he said, "I'm hoping to see some actual phones."

Greengart also said he expected AT&T to announce Palm phones at the show. Neither Palm nor AT&T has commented on any announcements.

The analyst said AT&T would be an important customer for Palm as the handset maker has struggled with weak sales.

"Palm certainly needs all the distribution it can get," Greengart said.

Sprint shares closed up 16 cents, or 4.6 percent, at $3.61 on the New York Stock Exchange. (Reporting by Sinead Carew, editing by Leslie Gevirtz)