AT&T Inc. plans to start selling a fast-speed smartphone made by Nokia Oyj, its first handset running Microsoft Corp.’s Windows Phone software that will work on the new LTE network technology. Stephen Elop, Nokia’s chief executive officer, made the announcement today at the Consumer Electronics Show in Las Vegas, without giving pricing or availability details. AT&T is expanding its LTE, or Long-Term Evolution, network and adding devices to catch up with larger rival Verizon Wireless, which has offered LTE devices for longer. The new device is also a step in Microsoft’s plan to fight Apple Inc. and Google Inc. in the mobile-phone market