Apple announced on Friday that the Wi-Fi versions of its long-awaited iPad will arrive April 3 in stores in the United States. The models that can tap into AT&T’s 3G wireless data network will be available in late April.

Customers can pre-order the iPad on Apple’s Web site beginning next Friday.

Apple’s tablet computer is expected to ship with 12 new applications designed specifically for the device, and it will run almost all of the more than 150,000 applications available for the iPhone and iPod Touch.

Apple has been aiming the iPad squarely at e-book readers like Amazon.com’s Kindle. And in its news release Friday, Apple said that an updated version of its iBooks app that will include Apple’s iBookstore will be available as a free download on April 3 in the United States, with additional countries to be added later.

The company has been aggressively recruiting personnel for the new iBookstore, listing a variety of iBook-related job openings on its corporate job board — including “Manager, iBooks Asia Pacific & Canada,” “Independent Publisher Acct. Mgr., iBookstore” and a “Merchandising Manager, iBookstore.”

Apple said that pricing for the device will be the same as it initially announced in January:

iPad will be available in Wi-Fi models on April 3 in the United States for a suggested retail price of $499 for 16GB, $599 for 32GB, $699 for 64GB. The Wi-Fi + 3G models will be available in late April for a suggested retail price of $629 for 16GB, $729 for 32GB and $829 for 64GB. iPad will be sold in the United States through the Apple Store (www.apple.com), Apple’s retail stores and select Apple Authorized Resellers.

Apple said the iPad will be available in both Wi-Fi and 3G models in late April in Australia, Canada, France, Germany, Italy, Japan, Spain, Switzerland and the United Kingdom, with more countries added later this year.