Google Inc. has opened it instant messaging and Internet telephony services to any company willing to support the XMPP protocol, a standard under the control of an open-source foundation.

XMPP, or extensible messaging and presence protocol, is an XML-based protocol for passing instant messaging and presence information among servers. The protocol is under the Jabber Software Foundation.

Google said on its Web site that it's committed to taking an "open federation" approach to instant messaging and Internet telephony, which means people on its networks can communicate with anyone on a system supporting XMPP.

By taking this step, Google hopes to move the industry "one step closer to making IM and Internet voice calling as ubiquitous as email," the company said, noting that XMPP is supported by Earthlink, Gizmo Project, Tiscali, Netease, Chikka, MediaRing, and "thousands of other ISPs, universities, corporations and individual users."

Missing, however, are rivals Yahoo Inc. and Microsoft Corp. Neither of their IM or VoIP systems communicates with Google's.

But there has been movement among the competitors toward interoperability, primarily through alliances of self-interest.

Google and America Online Inc., which operates the largest IM network in the United States, have agreed to allow cross-communication. The deal was part of Google's agreement late last year to invest $1 billion in AOL, which is a unit of Time Warner Inc.

Microsoft and Yahoo have said they plan to let IM subscribers communicate across their IM and VoIP networks in the second quarter of this year. The combined networks in the U.S. would be close to the size of AOL's.