Customers try out Apple's new iPad in a shop in May 2010. Apple on Monday promised that US orders for its iPad tablet computers would ship within 24 hours, in a sign that supply of the hot-selling devices was catching up to demand.

Apple on Monday promised that US orders for its iPad tablet computers would ship within 24 hours, in a sign that supply of the hot-selling devices was catching up to demand.

The online indicated that any of the six models would be shipped, free of charge, within 24 hours of an order being placed.

People have snapped up millions of iPads since the launched in the United States and wait times for the devices at times stretched into weeks.

The shortened wait has prompted debate over whether Apple's beefed-up production was paying off or if demand for iPads was waning.

Apple could provide some perspective on iPad sales during a special event to take place in San Francisco on Wednesday, but the California company's iPod line is expected to be the main focus of the gathering.

The iPad went on sale in the United States on April 3 and Apple sold more than three million in 80 days.

The iPad allows users to watch video, listen to music, play games, surf the Web or read electronic books. The cheapest iPad costs 499 dollars (US) while the top model is priced at 829 dollars.

Apple has released the iPad in more than a dozen countries, and China Unicom is expected to start selling Apple's iPad in the world's largest Internet market in mid to late-September.