Google Inc. and Sun Microsystems Inc. Tuesday unveiled a collaborative effort to promote Sun"s open-source software, a move that will make it easier for users to freely obtain Sun"s Java Runtime Environment, the Google Toolbar and the OpenOffice.org productivity suite, the companies said at an afternoon news conference. Terms of the agreement were not disclosed.

Under the deal, Sun will include the Google Toolbar as an option in its consumer downloads of the Java Runtime Environment. In addition, the companies have agreed to explore opportunities to promote and enhance Sun technologies, like the Java Runtime Environment and the OpenOffice.org productivity suite.

"Working with Google will make our technologies available more broadly, increase options for users, lower barriers and expand participation worldwide," said Scott McNealy, Sun"s CEO.

The move is expected to be part of a larger technology initiative in which Sun will help Google build a network to provide Web-based applications that will enable them to compete with their common rival, Microsoft Corp.

"We look forward to exploring other related areas of collaboration," said Google"s CEO, Eric Schmidt.

Although neither company mentioned Microsoft by name during the news conference, industry sources have speculated that Google is interested in offering more Web-based applications as a way to compete with Microsoft.

Microsoft has made no bones about its aim to unseat Google as the leading search-engine company and has said it will begin offering more services in the next year.

Sun, too, sees Microsoft as one of its chief rivals in the software market but has been having trouble garnering widespread adoption of its software portfolio, including its StarOffice productivity suite. The company just released a new version of StarOffice, which is based on the open-source OpenOffice suite and provides improved interoperability with Microsoft Office.

Sun also believes it has momentum for StarOffice thanks to a recent decision by the state of Massachusetts to move to open office file formats for documents created by its government agencies. The state plans to support the newly ratified Open Document Format for Office Applications, or OpenDocument, as the standard for its office documents. Suites that support OpenDocument include OpenOffice, StarOffice, KOffice and IBM Workplace. Microsoft Office does not support the file format.

A pairing of Sun and Google, then, could give Google the technology it needs to rival Microsoft in providing applications as services while giving Sun an edge in the applications business as well.

Despite Tuesday"s announcement, widespread adoption of Sun"s technology -- especially by business users -- may not happen anytime soon, according to Roger Kay, an analyst at Endpoint Technologies Associates in Concord, Mass.

"There are compatibility issues -- there"s not a 100 percent matchup between Microsoft"s Word and OpenOffice"s word processing program. If you format a document in Word and open it in OpenOffice, you"ll see the text but you may not see all the formatting that was done in Word, and I believe the reverse is true," Kay said. "The reason that all the commercial customers all use Office is because everybody else has Office. It"s not because they love its features. What they really care about is compatibility, and not just compatibility with other people they might exchange documents with but with their own history and other people"s history."

Businesses just can"t throw compatability out the window, he said.

"They can"t say this is better stuff. There has to be a way to get back and forth to all that history. So if you don"t have that kind of ability to read formats back and forth, then you have to have a filter system," Kay said. "So I believe any assault on [Microsoft] Office has to deal with these questions: What are you going to do about that compatibility, and how are you going to handle the filtering to get between document types?

"Those are old subjects that have been around for a long time, and they have not been solved to anybody"s satisfaction," he said. "That"s why Office has come to dominate. Because sometimes there is a natural monopoly in commercial productivity software. But there are these transactional customers that don"t necessarily care about compatibility, particularly consumers and small business."

Nevertheless, Microsoft should be worried, Kay said.

"If these guys establish a beachhead, that gives them a chance to build out from there, and Google has a lot of momentum. If they are successful in creating any alternative to Office, then that"s potentially worrisome for the longer haul," he said. "But in the short term, the fat middle of Microsoft"s market is safe."

Elizabeth Montalbano of the IDG News Service contributed to this report.