The iPhone 4 is now available in the United States through Apples online store without the need to sign a multi-year contract with a carrier.

Apple is selling the (32GB) white and black versions of the device for $749; the 16GB versions cost $649.

The devices will ship within one to three business days. Orders placed through the Apple store can only be shipped within the country where it is purchased.

If you dont want a multiyear service contract or if you prefer to use a local carrier when traveling abroad, the unlocked iPhone 4 is the best choice,” Apple explains on its website. It arrives without a micro-SIM card, so youll need an active micro-SIM card from any supported GSM carrier worldwide.”

For practical purposes, the “unlocked” iPhone 4 wont give people in the U.S. many choices of mobile operators.

In the U.S., only AT&T and T-Mobile USA support GSM (Global System for Mobile Communications) an industry standard used by many operators around the world.

Verizon Wireless, which uses a different technology known as CDMA (code division multiple access), began selling the iPhone 4 earlier this year, ending AT&Ts exclusive right to sell the iPhone.

Setting up the unlocked iPhone 4 appears to be relatively straightforward.

The unlocked iPhone 4 requires an active micro-SIM card that you obtain from a supported GSM wireless carrier,” Apple states. Simply insert the micro-SIM card into the slot on our iPhone, connect to your Mac or PC using the USB cable, and launch iTunes on your computer to complete the setup.”