Google and Sun Microsystems have joined forces to challenge the dominance of Microsoft's Office software.
Sun and Google are hoping for a flush fit
Google aims to "explore opportunities to promote" Sun's OpenOffice software. Those downloading Sun's Java program will be offered Google's toolbar.
Word processing and spreadsheet products are some of Microsoft's biggest sales generators, earning the company $11bn (£6.3bn) last year.
Microsoft is feeling pressure as firms offer cheaper or free rival products.
One of the biggest challenges facing Microsoft, the world's biggest software company, is convincing customers to pay for bundles of software like Office and Windows when they can find cheaper or free versions elsewhere.
Companies like Google and Sun, meanwhile, are looking to eat further and further into Microsoft's market share.
"Working with Google will make our technologies more available more broadly, increase options for users, lower barriers and expand participation worldwide," said Scott McNealy, Sun's chief executive officer.
Sun has long supported plans to create more open source software.
The deal may prove to be the first of many projects, the firms said.
Google chief executive Eric Schmidt described the arrangement with Sun as "a very significant deal".
"Google and Java are two of the most widely recognized technology brands because they provide users with online tools that enhance their lives on a day-to-day basis," said Mr Schmidt.
"We look forward to exploring other areas of collaboration."
Java software is needed to run a variety of Web applications.
At the close of trade in the US on Tuesday, shares in Google were down almost 2.5% at $311. Shares in Sun Microsystems closed up almost 0.25% at $4.20.