Google and Sun Microsystems have clarified their tactics for jointly attacking Microsoft Corp and its Office software. Google quietly began including Sun's StarOffice suite of word processing, spreadsheets and other workplace-oriented programmes for free as part of the Google Pack download.

The download package is part of Google's efforts to expand beyond Web search and control more of users' computing experience online and offline. It already includes Firefox, the No 2 Web browser behind Microsoft's Internet Explorer, and RealNetworks Inc's RealPlayer, a key rival to Microsoft's own media player.

By adding Sun's software, Google is giving a valuable endorsement to a server and software maker that saw demand for its products collapse after the dotcom bust and has struggled to return to sustained profitability ever since. StarOffice is Sun's commercial version of the freely distributed OpenOffice suite, which also was developed by Sun and has been downloaded about 100 million times. StarOffice typically costs $70 to download but is being distributed by Google for free. It has more features than OpenOffice and typically includes technical support from Sun, though the free Google version won't.