SAN FRANCISCO: IBM, whose secure messaging system is used within many of the biggest companies, on Monday said its customers would soon be able to chat with instant messaging users from America Online, Yahoo and Google.

International Business Machines Corp. said it plans by midyear to allow its Lotus Sametime corporate instant messaging system to work with the three consumer platforms, marking the latest move to break down barriers that have separated instant messaging audiences from one another.

Missing from the deal is Microsoft Corp., the most direct rival of IBM in the corporate instant messaging world, where customers often demand greater security and the ability of managers to audit what users say.

Lotus Sametime counts 20 million users inside companies worldwide, including more than 25 companies with over 100,000 users apiece. IBM said 60 percent of the world's 100 largest companies use Sametime.

America Online's AIM, the most popular instant messaging system, has more than twice as many users, or more than 40 million in the United States alone, a comScore Media Metrix survey showed.

Yahoo had roughly 20 million users, and Microsoft had around 15 million users, according to mid-year 2005 data. Google had far fewer users, having only introduced IM midway through 2005.

By allowing corporate messaging systems to work with consumer versions of IM, office workers will be able to communicate instantly with friends or family outside of work.

The ability to interconnect the separate instant messaging systems of IBM, AOL, Yahoo and Google is based on an industry standard technology known as Session Initiation Protocol, or SIP.

The computer company also said it planned to incorporate "click-to-call" Web-based calling and videoconferencing features into Sametime through deals with Avaya, Nortel, Polycom, Premiere Global Services, Siemens AG and Tandberg ASA.

IBM made the announcements at Lotusphere, the annual conference it holds in Orlando, Florida, to discuss innovations in its corporate mail, messaging and collaboration software.

IBM said its Lotus business, which has been losing market share to Microsoft Outlook/Exchange in the broader field of corporate e-mail systems, nonetheless enjoyed 10 percent growth in 2005 -- its first year of double-digit growth in a decade.

Lotus Notes counts 120 million users of the e-mail and document management system, according to industry data.