AOL Offers Plan to Link Its Messaging System With Rivals’

America Online Inc., the world’s largest online service, said it submitted a proposal to an Internet task force outlining how it could make its instant-messaging system work with competing systems.

The Federal Communications Commission, in reviewing America Online’s planned $139-billion acquisition of Time Warner Inc., had asked the companies to address concerns raised by rivals regarding America Online’s practice of blocking instant messages from consumers using other software.

The company said it submitted a proposal to the Internet Engineering Task Force, a volunteer organization that makes recommendations on technology standards.

America Online’s instant-messaging service is free for anyone with an Internet connection. That has helped to more than double the service’s registered users to 91 million as of March from more than 45 million in August.

The FTC also is reviewing whether the America Online-Time Warner combination would violate antitrust laws.

Agreeing on a standard for the service could resolve a battle that started a year ago.

Microsoft Corp. and Prodigy Communications Corp., an Internet-access provider, in July tried to link their messaging services to AOL’s.

America Online blocked users of Microsoft’s program from linking to its service, arguing that Microsoft was asking AOL members to reveal their user names and passwords, jeopardizing security. Instead, AOL asked Microsoft and others for a “business arrangement” to resolve the battle.

Several Internet companies, including Internet-access providers Juno Online Service Inc. and EarthLink Inc. agreed to enter such an arrangement, so that their customers could message America Online’s subscribers. Terms of those agreements weren’t disclosed.

Shares of Dulles, Va.-based America Online fell 50 cents to close at $54.50 on the New York Stock Exchange.