It looks as if AT&T, the exclusive operator for the iPhone in the States, has been forced to put stock control measures in place in order to stretch out the availability of the Apple mobile until the 3G version launches, almost certainly in June.

An AT&T internal memo to its retail department on Wednesday has initiated some new policies regarding sales of the iPhone, mainly meaning customers are allowed to purchase only one of the handsets until further notice.

"Effective May 14, 2008, customers can only purchase one iPhone at AT&T stores. The prior limit of three iPhones is no longer in effect", reads the memo. Requests to purchase more than one must be approved by a director or general manager, and cash and cheque payments will no longer be accepted.

Apple's online stores in the US and UK are currently showing the iPhone as "unavailable" while here in the UK, operator O2 only has stock of the 16GB models available.