iPhone 4 now available for preorder from Apple, worldwide carriers

As was announced at the Worldwide Developers Conference last week, customers can buy a 16GB iPhone 4 with a two-year contract with AT&T in the U.S. for $199, while the 32GB model costs $299.

Last year's iPhone 3GS, available in an 8GB capacity, is also available for $99 with contract, and all three models deliver on the launch date of June 24. Preorders are limited to two per customer.

On the Apple online store, the white iPhone 4 is not available for preorder. In addition, the model with a white front and back cannot be secured for in-store pickup. On AT&T's site, the white iPhone 4 is listed as "coming soon."

Limited availability of the white iPhone 4 was revealed on Monday, when an internal memo from AT&T suggested that supplies would be scarce at launch. That memo said that while AT&T stores will take reservations for the white iPhone 4, it will not become available until later this summer.

Both the black iPhone 4 and 8GB iPhone 3GS can be secured via free shipping, or with in-store pickup for the June 24 launch.

While the iPhone remains locked to Apple's exclusive carrier partner in the U.S., AT&T, some international customers have the option of an unlocked handset. An unlocked iPhone costs £499 for 16GB and £599 for 32GB in the U.K, and €629 for 16GB and €739 for 32GB in France. It is also available unlocked and SIM-free in Canada.

The new iPhone will debut next week in the U.S., France, Germany, the U.K. and Japan. Apple has announced that the iPhone 4 international launch will ramp up to 87 total countries by September, its fastest global deployment of a new handset.