Apple is rumoured to be readying an iBook upgrade for its invitation-only press event on May 1.

Apple representatives have been unable to disclose details of what is to be announced, but the invitation did warn Apple's guests to expect "plural" announcements, Macworld has learned.

Reports have hinted that Apple may release a reconfigured iBook at the event. Some claim the proposed model will be a slimline iBook, with others positing the consumer portable may even host a DVD-ROM drive.

Missing iBooks CNet has reported dwindling stocks of iBooks in recent weeks, with US dealers unable to access supply. Bearing out this report, Apple's own US AppleStore is now listing all iBook models as "temporarily unavailable."

A UK dealer confirmed that there is "no stock in the channel" of iBooks in the UK, although he did say that some Key Lime iBooks remain available, but not in any significant quantity.

He told Macworld that the Apple market is busy at the moment: "Phones are ringing, we're making sales. It's far healthier than the PC market, so I'm not as upset with Apple as I sometimes am."

The UK AppleStore continues to claim that stocks are available.