Palm Inc. on Wednesday said it has started sales of its Treo mobile phone powered by Microsoft Corp. software. The device could help Palm compete against Research In Motion’s Blackberry for corporate customers. 

Palm’s Treo 700w device, introduced at CES, will run on Verizon Wireless’s high speed data network, using Microsoft’s Windows Mobile operating system. 

The phone and digital assistant connects to the Internet and handles e-mail. It includes a built-in 1.3 megabyte camera that offers better pictures than current Treo models. The Treo 700w is priced at about $400, depending on related service agreements.

Palm, which pioneered the handheld computing market, has faced stiff competition from Microsoft and Canada’s Research In Motion, maker of Blackberry wireless e-mail devices, which have become wildly popular among business professionals.

The new Treo could potentially open up a much bigger corporate market for Palm, thanks to Microsoft’s central role in the desktop computer software and back-office e-mail markets. 

Verizon Wireless is a joint venture of Verizon Communications Inc. and Britain’s Vodafone Group Plc.