Microsoft has committed itself to supporting Office on the Mac for at least the next five years, the head of the software giant's Macintosh Business Unit said this week.

Speaking during Apple CEO Steve Jobs' Macworld Expo keynote, MBU General Manager Roz Ho said the company had entered into an "official agreement" with Apple to "continue shipping new versions of Office for Mac for a minimum of five years".

"This commitment should leave no doubt in your mind that we're here to stay and in [this market] for the long term," Ho told attendees.

The deal marked "another milestone in our relationship with Apple", she said.

Ho also promised Universal versions of Office and Messenger, to allow them to run natively on Intel-based Macs and older PowerPC-equipped models. She also said Microsoft had worked to ensure existing versions of Office will run well in Mac OS X for Intel's PowerPC emulation engine, Rosetta, and pointed to updates for this in March.

Microsoft will also roll in support for Mac OS X's Sync services and Spotlight search technology in an upcoming update for Entourage, what is essentially is Mac version of Outlook.

Beyond the tweaks, the agreement will Apple is interesting, and may scotch rumours that Apple is working on a full-scale productivity suite to rival Office. Apple certainly has to have a contingency plan in place should Microsoft ever drop Mac support, but the agreement announced this week means it has five years to develop something of its own, or see how OpenOffice development proceeds.

Not that Microsoft is really likely to ditch the Mac version of Office in any case: it's too valuable a money spinner. Ho said 2005 had been the MBU's most successful year to date, and for that look to Office, effectively the only Mac software Microsoft actually sells. She also said the company would this month offer a 50 per cent discount on the product to anyone who buys a new Mac, which gives you an indication just how big Microsoft's Mac Office margins are. ®