Microsoft has left the Opera and Google Chrome browsers off of the list of those officially supported by its Web-based Office applications, which will be available worldwide in technical preview sometime this month.

In a blog posting on the Office Web Apps blog, Microsoft listed its Internet Explorer 7 and 8 browser as well as Mozilla Firefox 3.5 on Windows, Mac and Linux, and Safari 4 on Mac, as the official supported browsers.

Office Web Apps are Web-based versions of Microsoft's Word, PowerPoint, Excel and OneNote desktop applications.

Absent from that list are the Opera and Chrome browsers, which have significantly less market share than either Internet Explorer or Firefox but are still competitors in the global browser market.

Opera is the European-based browser company that was instrumental in the European Commission bringing an antitrust suit against Microsoft over the inclusion of Internet Explorer in Windows. The suit has caused Microsoft to pull Internet Explorer 8 out of Windows 7 in Europe and offer a choice of browsers in the OS.

Google, which makes Chrome, is one of Microsoft's main competitors, and recently unveiled a plan to build a desktop OS of the same name to compete with Windows.

In fact, Microsoft's decision to put its Office productivity apps online is due to competition from Google Docs -- Google's Web-based office suite -- in the low end of the market for productivity applications.

Microsoft did say in the post, attributed to Gareth Howell, program manager for Office Web Apps, that people should try using the applications in other browsers besides the officially supported ones, and provide feedback to the company about how they work.

"If you prefer to use another browser you should still give the Web Apps a try," he wrote in the post. "While we cannot officially support all browsers, customers will not be blocked from using them. It is a goal of the Web Apps to have broad compatibility and reach."

In comments about the blog post, one Opera user playfully chided Microsoft for not supporting Opera with the applications.

"Not MY browser then...**sniff**," posted a user called "Massif."

"That's fine, I'll be alright. Opera users need a little love too occasionally though, we can't live on acid tests alone."

Howell responded to Massif's post by apologizing and adding that Microsoft may consider officially supporting other browsers after the release of the applications.

"Sorry that we didn't get your favorite browser into the officially supported list this time," Howell posted.

"Once the Web Apps release we'll investigate expanding our supported browser matrix. Give it a try in Opera and let us know if you see issues."

Through its public relations firm, Microsoft said the company optimized Office Web Apps for the most commonly used browsers and plans to add others over time.

Opera spokesman Ted Miller said via e-mail that, based on Howell's comments, Opera is "encouraged" by Microsoft's commitment to troubleshoot compatibility issues that Opera browser users may encounter.

He added that Opera is willing to work with Microsoft to ensure a smooth Office Web Apps experience for users of browsers not officially supported by the applications.

Google did not immediately respond to a request for comment.