Clearwire, which has set out on an ambitious build-out this year of its 4G wireless data service, added on Tuesday more cities to its list of places that the company plans to make its WiMax service available.

Clearwire, majority owned by Sprint Nextel, said Los Angeles, Miami, St. Louis, Cincinnati, Cleveland, Pittsburgh, and Salt Lake City would be covered by the end of the year. Earlier this year, Clearwire announced plans for WiMax in New York, Boston, Washington D.C., Houston, the San Francisco Bay area, Denver, Minneapolis, and Kansas City.

Today, 27 cities have Clearwire services. By the end of the year, the company hopes to be able to reach 120 million people.

Clearwire's service today is available via external modem or a WiMax-to-Wi-Fi router. There are also a growing number of devices available with built-in WiMax technology, thanks to a major push by chipmaker Intel. Clearwire counts a total of 30 4G-ready netbooks and laptops available from Dell, Lenovo, Fujitsu, Samsung, and Toshiba.

On Tuesday, Clearwire announced one more WiMax-ready device, saying Dell planned to release the Inspiron Mini 10 netbook on April 1.

Clearwire has a head start over competitor Verizon Wireless, which is getting ready to launch its LTE 4G network later this year. Clearwire is hoping to best its larger rival with the help of its cable TV investment partners, including Comcast, Sprint, and Time Warner Cable. The three companies would resell Clearwire's service.

Clearwire made its latest announcements at the International CTIA Wireless show in Las Vegas. The company is expected to introduce at the event a dual-mode 3G/4G smartphone that would be available this summer. If that happens, then the handset would be released well ahead of any LTE mobile phone from Verizon Wireless.

In February, Clearwire reported strong subscriber gains in its last quarter, saying the additional 87,000 retail subscribers outpaced growth in the company's first three quarters combined. Nevertheless, Clearwire reported a loss of $90.4 million on revenue of $79.9 million.

In general, WiMax offers faster download and upload speeds than today's 3G networks. However, like the latter, WiMax service is inconsistent, with speeds varying dramatically throughout the day depending on network traffic and other factors, tests show.