SAN FRANCISCO - Apple fans flocked online Friday to be among the first to order iPad tablet computers slated to begin shipping in the United States on April 3.

Apple was offering free shipping on pre-orders but limited buyers to no more than two iPads each in a sign that supplies will be tight when the iconic company's latest creation hits the market.

Apple chief executive Steve Jobs unveiled the iPad in San Francisco on January 27, billing it as a "revolutionary" device that will carve out a home between smartphones and laptop computers.

The iPad allow users to watch video, listen to music, play games, surf the Web or read electronic books.

The iPad also runs most of the 150,000 applications made for the iPod music player and the iPhone. Apple has promised that the device would come with "12 new innovative apps designed especially for iPad."

The iPad model featuring Wi-Fi wireless connectivity will be available in Apple's US stores from April 3 and the model that offers both Wi-Fi and 3G cellular connectivity in late April, Apple said.

The company said both the Wi-Fi and 3G models will be available in Australia, Britain, Canada, France, Germany, Italy, Japan, Spain and Switzerland in late April and in additional countries later this year.

Apple said international pricing will be announced in April.

"We're excited for customers to get their hands on this magical and revolutionary product and connect with their apps and content in a more intimate, intuitive and fun way than ever before," Jobs said in statement last week.

Morgan Stanley analyst Katy Huberty forecast iPad sales of six million units this year, a figure she acknowledged was above the "consensus" of between three and four million units.

The iPad has a 9.7-inch (24.6-centimeter) color screen and resembles an oversized iPhone. It is 0.5 inches (1.3 centimeters) thick, weighs 1.5 pounds (0.7 kilos) and comes with 16, 32, or 64 gigabytes of memory.

Apple has been pushing the iPad's abilities as an e-book reader and analysts have described the color screen device as a potential rival to Amazon's Kindle.

Apple said its new iBookstore will include books from the New York Times best-seller list and a number of publishers including Hachette, HarperCollins, Macmillan, Penguin and Simon & Schuster.

The cheapest iPad model, with Wi-Fi connectivity and 16GB of memory, is 499 dollars (S$700) while the most expensive - which includes 3G connectivity and 64GB of memory - costs 829 dollars.

Reviewers have been mixed on whether the iPad will be a smash hit like the iPod, which controls over 70 percent of the market for MP3 players, or the iPhone, which completely transformed the smartphone arena.