Microsoft and Orange will link their instant messaging systems later this year, allowing up to 375 million people to chat with each other using their PC or mobile phone.

Orange will offer its French mobile phone and Internet access customers a new service in December called Orange Messenger by Windows Live. It will extend the service to the U.K. and Spain next year, making it accessible to 135 million Orange customers in total, the company said Wednesday. Microsoft puts the number of Windows Live Messenger customers at 240 million.

Steve Ballmer, Microsoft's CEO, was in Paris Wednesday morning to make a formal announcement with Orange executives.

Orange already offers an IM service called Orange Messenger. The link between the two companies' services will allow Orange customers to exchange IMs with customers of other networks that use Windows Live Messenger. In France they include mobile virtual network operator Ten, and GSM operator Bouygues Telecom.

The link-up will also allow Orange and Windows Live users to video-conference from their PCs, and send SMS text messages from their PC to mobile phone users.

France Telecom, the parent of Orange, recently rebranded its Internet service operations as Orange, which is also the name of its mobile business. The Internet access service was previously known as Wanadoo.

The IDG News Service is a Network World affiliate.