Microsoft Corp. and Yahoo Inc. have reached a deal to make their two instant messaging programs work together, in a partnership that could provide a challenge to market leader America Online, people familiar with the situation said Tuesday. The deal was expected to be announced early Wednesday, the two sources told The Associated Press. One of the sources works closely with Microsoft and has been involved in company discussions. The other is familiar with the deal. Both spoke on condition of anonymity. The agreement would allow users of both services to send and receive messages, regardless of which system they were using. Previously, the systems did not work with each other. Microsoft has long sought to forge some sort of deal to boost the profile of MSN Messenger. The company also has been in talks with AOL over possible partnerships with Microsoft's MSN online unit, although it's not clear where those talks stand now. Spokesmen for Microsoft, Yahoo and AOL declined to comment.