Barriers between instant messaging products are proving hard to dismantle, sparking new tactics in a brewing standards war over the nascent technology. Talks held by the Internet Engineering Task Force (IETF) that aimed to set technical specifications allowing rivals such as AOL Time Warner, Microsoft, Yahoo and others to develop a joint IM platform have stalled, according to people close to the discussions. AOL Time Warner, the leader in instant messaging, says it is continuing to work on solutions to connect its AOL Instant Messenger (AIM) and ICQ services to competitors but that it has no firm deadline for implementation. Meanwhile, an independent effort to connect incompatible services this year by a coalition of AOL Time Warner competitors, known as IMUnified, has run into delays. "In retrospect, it was unrealistic," one executive in an IMUnified company said about the time frame to launch the standard. The quest for interoperability has driven the IM market ever since competitors first stepped forward to challenge AOL Time Warner for control of one of the fastest-growing technologies on the Net. But now, in a sign that frustrations over cooperation are fading, IM developers such as Microsoft are moving ahead with independent plans for the technology, leaving AOL Time Warner and others to go their own way or follow their lead. In the strongest sign yet that Microsoft is preparing to provide a broad platform for IM standards, the company this week unveiled Windows Messenger, a product that offers chat, multimedia, conferencing and telephony features that wrap around any IM product. "From a strategic standpoint, IM providers will certainly want to work with any underlying protocol that Microsoft would want to support without question because of their strength in the marketplace," said Alex Diamandis, an executive at rival IM company Odigo. AOL Time Warner "doesn't have the ability to do what Microsoft can do, which is to embed it into all of these other applications -- embed it into Outlook, embed it into Office, embed it into browsers, and on and on." The strategy reflects significant changes in the marketplace from a year ago. Although AOL Time Warner still leads with the combined use of its separate AIM and ICQ networks, Microsoft has presented evidence that its MSN Messenger service is the single-most widely used IM service. Perhaps more importantly, Microsoft is feeling new confidence with the upcoming October release of its Windows XP operating system that it can drive standards single-handedly by expanding the features supported by instant messaging and encouraging developers to build to its specifications. Microsoft spokesman Jim Cullinan confirmed the company's open platform is an intentional contrast with AOL Time Warner's proprietary approach. "The question you need to ask is, 'Where is the value of developers?'" he said. " Do they want to call on things that are in Windows XP, in AOL or in Linux? That's up to the developer. So from our point of view, we're always considering how to provide excitement for developers." Although IMUnified may be stalled and its loudest voices quieted, Microsoft has continued to play two decks in pushing for standards. Besides its commitment to IMUnified, Microsoft has put its weight behind a technology called SIP (session initiation protocol). SIP is a road map that allows computer servers to exchange information with each other. It is also the protocol behind how people using the new Windows Messenger can communicate in real time. Microsoft's MSN Messenger has its own proprietary protocol, which only lets people using its service communicate with each other. But there remains a possibility in the future for MSN Messenger to also use SIP as its protocol, allowing both products to evolve more closely together. Already, Windows and MSN messenger users will be able to chat with each other through text. But for now, the two services are different. Windows Messenger lets Windows XP users to communicate with each other through video, telephony and audio. MSN Messenger remains a text-based service. "On some level these two will always be kissing cousins, but Windows Messenger offers added value that's a superset of MSN Messenger features," said Tom Laemmel, a product manager for Windows. Meanwhile, efforts to establish compatibility for competing IM services are continuing on several fronts, according to participants, although progress has been stymied to date. "We are on track to begin testing a possible solution this summer and continue to be committed to interoperability to protect consumers' privacy, security and system performance," said Kathy McKiernan, an AOL spokeswoman. IMUnified, whose member include Microsoft, Yahoo, AT&T, Excite@Home, CMGI and Odigo, is still pushing to establish interoperability among its members, according to representatives. "We are still working together and expect to make an announcement on reaching interoperability later this year," said Estela Mendoza, a spokeswoman for IMUnified and Excite@Home. Mendoza attributed the delays to continued technical issues, where companies are trying to flush out "kinks" in the system. Other members of the coalition have blamed a host of other issues for the delays. The most vocal members of the group represented by CMGI-owned Tribal Voice and iCast both were shut down after their parent company restructured its holdings. Meanwhile, Odigo's Diamandis said the technology behind IMUnified's standard has been operational for months, but getting all of the players to sign off on it has been difficult. Diamandis noted that the IMUnified was created as a temporary solution to circumvent AOL Time Warner and that companies would likely adopt the standard approved by the IETF. The standards task force, for its part, continues to be at a standstill in choosing an appropriate standard for IM interoperability. "The reality is we're not necessarily much further than we were a year ago," said Andre Durand, general manager of Jabber, which makes Linux-based IM servers. Have your say instantly, and see what others have said. Click on the TalkBack button and go to the ZDNet news forum. Let the editors know what you think in the Mailroom. And read other letters.