America Online Inc is to extend its Instant Messaging technology for Macintosh following a deal with Apple Computer Inc announced yesterday. The development will enable seamless communication between Mac users and the AOL AIM Instant Messenger service, the two said.

AOL is currently in the midst of an interoperability war with Microsoft Corp over Microsoft’s recently launched MSN Messenger software, which was written to enable users to connect to AIM. But AOL blocked the communications capabilities of the initial build within hours, and continues to block the new builds Microsoft is now issuing on a daily basis. AOL had reached its sixth block at the last count. Despite this, Microsoft says it has now reached over 700,000 unique users, and has had over a million downloads, including duplicates for the new builds. AOL claims 40 million registered users of its Buddy List and AIM services, and says it has signed 25 million over the last six months.

Microsoft says it is also working on a Macintosh version of MSN Messenger, which is expected to emerge over the next three months.