Apple has delayed the launch of the iPad, which promises to greatly expand the functionality of e-readers. The tablet, originally scheduled for worldwide release in March, will hit U.S. stores on April 3, according to the AP. Apple said Friday that Wi-Fi models will go on sale first; iPads that can connect to Wi-Fi and 3G cellular networks will go on sale in late April. The iPad, which features a touch screen similar to the iPhone, will cost between $499 and $829, depending on the features included.