Some US Apple retail stores have reportedly begun selling iPhone 3Gs without a contract. Apple Insider reports the 8GB model is available for $599 and the 16GB for $699, the standard retail price without AT&T subsidies.

The iPhones are still locked to AT&T service, but third-party unlocking tools could theoretically allow the phones to work with other GSM carriers including T-Mobile and Metro PCS. However, those networks do not support the higher 3G data speeds offered by AT&T.

Thursday’s news comes on the same day AT&T planned to start selling iPhones without a contract to existing iPhone users, with a one-per-customer limit. According to AI, Apple retail stores have no such restrictions. The new policy could be an attempt to sell off the remaining inventory of the current iPhone 3G model to make room for a new version. There is no word whether all U-S Apple Stores are selling the contract-free models or if the supply is limited to a few stores.