Apple started selling the factory-unlocked GSM iPhone 5 models on its Online Store in the U.S. Thursday night.

The unlocked GSM iPhone 5 is available at a price of $649, $749 and $849 for the 16, 32 and 64 GB models respectively. The shipping time is estimated to be one week. The unlocked models will function on both AT&T and T-Mobile.

A statement on Apple's official site said: "The unlocked iPhone includes all the features of iPhone but without a wireless contract commitment. You can activate and use iPhone on the supported GSM wireless network of your choice, such as AT&T in the United States. The unlocked iPhone 4, iPhone 4S and iPhone 5 will not work with CDMA-based carriers such as Verizon Wireless or Sprint.

If you don't want a multiyear service contract, or if you prefer to use a local carrier when traveling abroad, the unlocked iPhone is the best choice. It does not come with a micro-SIM card for iPhone 4 and iPhone 4S, or a nano-SIM card for iPhone 5, so you'll need to get one from any supported GSM carrier worldwide. To start using it, simply insert the card into the slot on your iPhone and turn it on by pressing and holding the On/Off button for a few seconds. Then follow the onscreen instructions to set up your iPhone."

The launch of the unlocked iPhone 5 was delayed in the U.S. as in the case of iPhone 4S.

9To5Mac reported, quoted "several retail sources," that Apple would soon sell the unlocked iPhone 5 models in its chain of retail stores, perhaps as soon as Friday. The report also included, "The devices have begun arriving in large quantities over the past couple of days to Apple stores."

It is also said that Apple is likely to expand its Personal Pickup program for iPhone5 which will allow the customers to reserve a device at any time, not just after 10 p.m., for pickup the next day.