Yahoo! ( YHOO) and Microsoft ( MSFT) will begin limited public beta testing of interoperability between their instant messaging services.

The companies announced late Wednesday the plan will allow users of Microsoft's Windows Live Messenger, the next generation of MSN Messenger, and Yahoo! Messenger with Voice to connect with each other. This interoperability will form the world's largest consumer IM community, approaching 350 million accounts, the companies said.

Consumers worldwide from Microsoft and Yahoo! will be able to take advantage of IM interoperability and join the limited public beta program. The companies plan to make the interoperability between their respective IM services broadly available to consumers in the coming months.

"This first-of-its-kind interoperability between consumer IM leaders Microsoft and Yahoo! gives our customers tremendous control, convenience and freedom in their Web communication experiences with Windows Live," said Blake Irving, corporate vice president of Windows Live Platform at Microsoft. "We're proud to deliver this latest advancement in IM services that empower people to communicate with virtually whomever they want, wherever they want and whenever they want."