Microsoft Exchange Server 2007 is also expected for release in late 2006 or early 2007, and Microsoft Speech Server 2007 will be available in late 2006, Microsoft said in a statement Monday.

Microsoft's unified communications strategy involves partnerships with other communications vendors and includes plans for IP desktop phones that run Communicator software. The vendors named were Polycom Inc., LG-Nortel Co. Ltd. and Thomson Telecom. Microsoft also announced interoperability with or partnerships with Hewlett-Packard Co., Siemens and Motorola Corp.

Zeus Kerravala, an analyst at Yankee Group Inc. in Boston, said that the main question about the company's unified communications products is whether they will be ready for corporate use when released.

"Buyer beware," Kerravala said. "When has Microsoft ever entered a market with a business-ready product out the door? They eventually get it right, but the first versions are usually not corporate ready. Think back to the Microsoft proxy server, their firewall, Exchange and directory services."

Even so, Kerravala said Microsoft's plans show it could become "a huge threat to all the VOIP competitors." Within a few years, Microsoft could join Avaya Inc. and Cisco Systems Inc. in owning about 90 percent of the VOIP marketplace, he said.