Microsoft has pushed back the release of Office 2008 for Mac, from the second half of this year to next January because it wasn't satisifed with the product.

"We had hoped to hit the Christmas selling season, but now we hope to target Macworld", said Craig Eisler, who became general manager of the Mac business unit at Microsoft six weeks ago. "We, as a group, were not satisfied with product quality."

MacWorld is due to run from 14-18 January 2008 in San Francisco.

Details about any software development snags, as well as final pricing, were unavailable. Office for Mac 2004 is sold in three versions priced from US$150 to US$500.

The company demonstrated early previews of Office 2008 for Mac at the Macworld 2007 convention.

Microsoft will not open beta testing to the public as it did for more than six months while building Office 2007 for Windows.

The 2008 release will be the first built for Intel-based Macs. The features and visual style of Office for Mac software differs from Windows versions.

Microsoft is introducing XML-based file formats, which require a converter to be opened in older Office software. A time management, task-launching widget becomes part of Office 2008 for Mac in addition to Word, Excel and PowerPoint and the Entourage e-mail application.

Among the controversial anticipated changes is the removal of Visual Basic scripting, which enables macros that automate commonly used software functions.

Microsoft postponed its initial shipment deadlines for Windows Vista and Office 2007, which arrived in stores on 30 January.

Microsoft aims to unveil its next operating system, internally code-named "Windows 7", within three years.

Meanwhile, Apple is tightlipped about the timing and features of its next iWork office suite, a competitor to Microsoft Office.

The MacRumors blog speculates that Apple may skip a 2007 version, instead releasing iWork '08 in October in tandem with the Leopard Mac OS X operating system.

Further competition to Microsoft Office and iWork looms in the form of free Web-based productivity software, such as Google Docs & Spreadsheets.