Sources: Apple Newton-tablet not ripe for Macworld

The project, however, remains a work-in-progress, according to people familiar with the matter, who attribute its floating timetable to a number of challenges similar to those that threatened to plague iPhone in the months leading up to last year's expo.

In its current form, the Newton device — sometimes dubbed a Mac tablet or slate — has been described along the lines of a larger iPod touch or iPhone rather than an Apple adaptation of the modern day tablet PC.

When the project does come to fruition, it's expected to leverage a more advanced implementation of Apple's multi-touch technology, featuring concepts and functionality not yet available on the company's iPhone and iPod touch handhelds.

Apple is instead expected to use next week's Macworld Expo to focus on Mac notebooks, iTunes content distribution, and iPhone advancements.

Among the specific announcements believed to be on tap are a chic and ultra-lightweight sub-notebook, a new iTunes movie rental service, and an updated version of the iPhone software.

It remains unclear whether Apple will make any announcements related to its planned adoption of the Intel Silverthorne ultra-mobile processor, as that chipset is neither launched nor available in production quantities at this time.