AT&T announced Tuesday that it has “taken the steps necessary so that Apple can enable VoIP applications on iPhone to run on AT&T’s wireless network.” This means that iPhone users in the U.S. will now be able to use VoIP apps when they’re connected to AT&T’s 3G network, rather than just Wi-Fi.Voice over IP – VoIP – enables users to communicate with one another transmitting their voices as packets of data over a network. It’s become a handy way for businesspeople and others to stay in touch without running up huge long-distance phone bills.

But until now, VoIP on iPhone apps has been limited specifically to Wi-Fi coverage. That’s fine if you’re in a relatively uncongested public hotspot or at home or even at work, but not when you’re out and about, connected only using AT&T’s data and voice network. Then, standard calling rules apply.

AT&T president and CEO Ralph de la Vega said in announcing the new capability that the iPhone has “changed the game in wireless” since it was introduced two years ago.

“Today’s decision was made after evaluating our customers’ expectations and use of the device compared to dozens of others we offer,” said de la Vega.

AT&T informed Apple and the Federal Communication Commission (FCC) of its decision on Tuesday afternoon, according to a statement.