The iPad will go on sale in nine more countries -- Austria, Belgium, Hong Kong, Ireland, Luxembourg, Mexico, Netherlands, New Zealand and Singapore -- in July, and additional countries later this year, Apple said.
Earlier this month, Apple said it had sold a million iPads in the first 28 days. Supplies of the gadget have fallen short of demand, and Apple has imposed restrictions on the number a person can purchase.
"We ... are working hard to build enough iPads for everyone," Apple CEO Steve Jobs said in a statement.
The iPad is driving the burgeoning popularity of tablets, shipments of which could grow sixfold by 2014, IDC said in research released on May 20. Tablet shipments could total seven million by the end of this year, and top 46 million by 2014, IDC said.
The iPad is a handheld device with which users can view movies, surf the Internet, read e-books and play games. It has no physical keyboard, but one can be displayed on its 9.7-inch touchscreen display. It is 1.27 centimeters thick and weighs 680 grams.