A pop-up warning that has appeared with the latest build of iOS - 5.1.1 - hints that Apple is soon to introduce the possibility of making FaceTime video calls over 3G, perhaps for iOS 6.

Since its launch, FaceTime has been restricted to Wi-Fi use, meaning that video calls can only be made when iPhones and iPads are logged on to a broadband network. However, when trying to switch off 3G during a FaceTime call, a message now warns: "Disabling 3G may end FaceTime. Are you sure you want to disable 3G?"

This would suggest that Apple is at least trialling the service over a 3G network, and may be about to release the feature for public consumption.

In the UK, however, this could cause problems as many users are not signed up to mobile network packages with all-you-can-eat data plans. Using FaceTime video calling over 3G could seriously munch into the amount of data you have available and end up costing a fortune in overspill fees.

In addition, carriers themselves may be concerned at the demands 3G FaceTime use may put on their networks. They may even block or restrict its use.

As we expect to hear more on iOS 6 at the forthcoming WWDC in the middle of June, we shouldn't have to wait too long to find out.

What do you think? Would you like to FaceTime over 3G? Let us know in the comments below...