Microsoft has unveiled a stopgap file converter that allows Mac Office users to work with Office 2007 Word document files.

The beta application only converts .docx files - documents saved in Word 2007's new native Open XML format – into Rich Text Format documents, a format that can be opened by Word 2004 or Word v.X for Mac OS X. It supports only one-way conversion.

"We do not want to see you inadvertently mess up any critical documents you are working with," Geoff Price, of Microsoft's Mac Business Unit, said in a posting to the Mac Office blog. "When sending documents back to colleagues and contacts, we recommend saving to the default .doc format from Mac Word."

Microsoft's Mac developers went with a standalone converter rather than an add-on to Office to cut down testing time and allow the Office 2008 team to focus on the new suite. A final, integrated converter for Office 2004 will launch six to eight weeks after Office 2008 debuts, as Microsoft promised in January when it announced the new Mac bundle. A polished stand-alone converter will be released after that.

Updates to the beta this summer will add conversions for Excel and PowerPoint documents, said Price. He didn't specify dates.

Office 2008 for Mac, which Microsoft has pinpointed as a second half 2007 release, will use the same default Open XML file as Windows' Office 2007 applications. The new suite - the first written by Microsoft for Intel-based Macs and the last to support older machines running PowerPC processors - will also rely on an Office 2007's Ribbon-like interface.

The 25MB converter installation file can be downloaded from Microsoft's website.

See PC Advisor's Office 2007 review.