Although O2 and Apple have remained tight-lipped about sales in specific regions, chief executive Steve Jobs said recently that over four million units had been sold in the four countries where it is currently available.
Some analysts are predicting that Apple and its exclusive UK distributors, O2 and Carphone Warehouse, will soon reduce or even scrap the £269 upfront fee for the iPhone in an attempt to woo customers.
O2 is still upbeat about the iPhone's performance, claiming that that it has been its fastest selling product "by a significant margin" and has enjoyed unprecedented levels of customer satisfaction.
Many were disappointed by the lack of an announcement of a 3G version of the iPhone at Macworld last week, following rumours that one would be available later this year.