The deal is designed to shrink the gap between mobile phones and PCs, as subscribers will now be able to conduct real-time chats by voice or text on both platforms.

The service , dubbed Orange Messenger by Windows Live, represents yet another step toward converging mobile technology with computers.

"The European market generally is one of the most convergent on the planet," Microsoft CEO Steve Ballmer said during a news conference. "This is the first time that two leading software and telecommunications companies have joined forces to offer an instant-messaging service that can be accessed from both PC and mobile devices."

Connectivity 24/7

Joe Wilcox, an analyst at Jupiter Research, noted that MSN Messenger is already available on numerous platforms around the world, but he pointed out that the deal with Orange in Europe marks a further commitment on the part of Microsoft to create more and more mobile capabilities for the traditional PC.

"Most people don't carry around a PC," Wilcox quipped. "But they do carry cell phones." The launch of the new offering, he said, reflects both firms' ongoing convergence strategies.

The companies said that, once the new software is deployed in France, Britain, and Spain, they would look at offering other services, including video-conferencing on 3G-capable mobile phones.

"Our ambition is to offer simple convergent services, bringing our customers into the world of always-on connectivity ," said Didier Lombard, CEO of France Telecom, in a statement.

More Services Coming

Ian Fogg, a senior analyst with Jupiter Research, said that what will make the deal particularly interesting for users is that they will be able to track contacts online through a "buddy list," meaning that PC users will be able to text-message their contacts on mobile phones, and vice versa.

"The buddy list becomes a platform to enable carriers to generate new revenue," said Fogg, who also noted that other options, such as group video-conferencing, might not be too far off.

Yahoo, a major competitor to Microsoft in the instant-messaging space, already has partnerships with cellular providers BT in Britain and Buoygues in France for similar instant-messaging offerings.

The financial details of the Microsoft-Orange deal were not disclosed. But Ballmer did tip his hat at the news conference to some extent. "This is not about a licensing arrangement," he said. "We are coming together as two equal partners in sharing costs and revenues."