Microsoft CEO Steve Ballmer and Nortel CEO Mike Zafirovski are set to discuss the announcement at 12 p.m. (EST) Tuesday, according to a Microsoft spokeswoman.

In an online description of the announcement, Jeff Raikes, president of Microsoft's business division, said the two companies will partner immediately on research and development efforts.

The companies will collaborate on development of products for large companies as well as for wireless and wire-line carriers, Raikes said. Nortel also will have developers working alongside the unified communications team in Redmond, Wash.

He said the technologies will include products that complement the Microsoft Unified Communications Platform, including contact center applications, mission-critical telephony functions, advanced mobile capabilities and data networking infrastructure.

Unified communications is a term used by analysts and vendors to describe the combination of communications modes such as wired and wireless and methods such as e-mail, voice, video and instant messaging (IM).