REDMOND, Wash. (AP) _ Microsoft Corp. said Wednesday it would release code for its new Internet instant-messaging service to aid in development of an industrywide standard.

The move comes as Microsoft duels with America Online Inc. over instant messaging, which gives Internet users the ability to exchange real-time notes that pop up on the recipient's computer screen.

AOL's Instant Messenger service, which user base dwarfs Microsoft's MSN Messenger Service in number of users, has been refusing to allow Microsoft's subscribers to communicate with its own.

The code, or ``protocol'' release is significant because it will aid in development of a universal standard for Internet messaging, which could force AOL to comply, said Vijay Saraswat, co-chairman of the independent Internet Engineering Task Force's working group on messaging.

``In this spirit of open protocols that benefit the entire Internet community, we strongly encourage other vendors to publish their protocols,'' he said in a Microsoft release.

Microsoft has promised to release the code for its MSN Messenger Service to the group by the end of this month.

Since beginning its own service last month, Microsoft has been battling with AOL, which has about 43 million users to Microsoft's 1.3 million. Both services are free.

Earlier Wednesday, Microsoft announced that three internet services _ Prodigy, Tribal Voice, and People Link _ had agreed to give their users the ability to instantly exchange messages with MSN's users.