Apple Inc. (NASDAQ:AAPL) is expanding its iPhone offerings even further in the U.S. The company is now selling an unlocked SIM-free iPhone 5S, according to the Apple website. 9to5 Mac spotted the new addition.

Apple iPhone 5s

Why would Apple do this?

The main users who would benefit from an unlocked SIM-free iPhone 5S are those who travel or otherwise would just like an unlocked phone, perhaps to take to one of the many prepaid plans which are popping up in the U.S. This particular model will work on the T-Mobile and AT&T networks, and it does not require a contract with the carriers, making it an option for customers who want a prepaid plan.

The handset also works on a variety of other GSM networks in other countries, so U.S. residents who frequently travel outside the country can take their iPhone 5S with them and simply swap out the SIM card when they arrive in the other country.

Unlocked SIM-free iPhone 5S available in all models

Apple Inc. (NASDAQ:AAPL) is offering this new SIM-free iPhone 5S in 16 GB, 31 GB and 64 GB sizes. The prices for them are $649, $749 and $849, respectively. The unlocked iPhone 5S is available in the same gold, silver and space gray choices that the regular iPhone 5S models are offered in. They ship in one to two weeks direct from Apple’s website and are expected to be available to purchase in Apple retail stores over the next few weeks.

The fact that Apple Inc. (NASDAQ:AAPL) is now offering these unlocked iPhone 5S may demonstrate progress in the company’s efforts to battle supply constraints of the handset. There has been a SIM-free iPhone 5C since the handset launched two months ago. Also countries other than the U.S. have had their own unlocked iPhone 5S models for a number of weeks. It may be that the U.S. market, which is still largely post-paid, may have a smaller demand for the unlocked models.