"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.
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.