Apple has delayed its major Apple TV software update "a week or two", the company annnounced last night.

Admitting that the update, which should have gone live by now according to the schedule stated by CEO Steve Jobs during his Macworld Expo keynote, was "not quite finished" will be ready for the set-top box's Software Update facility "within two weeks", Apple said.

In addition to a variety of interface tweaks and, presumably, bug fixes, the new Apple TV code adds support for iTunes Movie Rentals, though only US Apple TV owners will be able to make use of it initially.

Regular, DVD-quality programming will be on offer to, CEO Steve Jobs said, at a lower price: $3.99 for new titles, $2.99 for old ones.

Viewers will have just 24 hours to finish watching a rented movie once they've started watching it. But they'll have up to 30 days to press Play before the content vanishes from the Apple TV's hard drive.

The downloads will incorporate a Dolby 5.1-channel soundtrack, and they'll also be available to Mac and PC users through iTunes in the usual way, and with the same restrictions. Jobs claimed movies can be watched almost as soon as they've started downloading.

Downloads can be sync'd to a PC- or Mac-hosted iTunes library and copied to a video-capable iPod or iPhone.

Apple described the system software update as "automatic", suggesting that, once it's posted, it'll be flagged up consumers as soon as they switch their TVs to the set-top box.