HP acquired webOS last April when it bought Palm for US$1.2 billion in a surprise move. HP's own handset business had not been doing particularly well and it saw Palm as a way to give itself a leg up -- even though Palm was not a market leader either.

It soon became clear HP was looking beyond smartphones, however. It said it would use webOS for its Web-connected printers, and as the iPad took off it saw opportunities there as well.

Wednesday's event was closely watched to see what kind of hardware HP rolls out to get the most out of webOS.

HP is entering a crowded field when it comes to tablets. Along with the mighty Apple iPad it will compete with devices based on Google's Android, the latest version of which, Honeycomb, will debut later this month in the Motorola Xoom tablet. That 10.1-inch device will retail for $800, according to a leaked Best Buy advertisement.

Research in Motion is also in the game with its PlayBook tablet, which runs its own BlackBerry software. There are also tablets based on Windows 7, though Microsoft has struggled to make an impression in the tablet market.