Microsoft Corp. and Yahoo Inc. are beginning a limited test of plans to make their instant messaging systems work together.

The much-vaunted pairing comes a bit later than the two companies had originally hoped. The project was delayed because Microsoft wanted to make sure the systems would work well with both companies' millions of users, Microsoft executive Blake Irving said Wednesday.

"It's not the technical difficulty of the service itself. It's the technical difficulty of the scale that we're trying reach," said Irving, a corporate vice president for the Windows Live Platform.

Microsoft, Yahoo test instant messaging partnership [seattlepi.nwsource.com]