picture-30AT&T, the iPhone’s exclusive wireless carrier in the United States, said it has paved the way for Apple to let voice-over-Internet-protocol apps like Skype run on its 3G network instead of only on nearby Wi-Fi connections.

VoIP technology allows voice calls to be treated as data, making them significantly cheaper per minute.

The “iPhone is an innovative device that dramatically changed the game in wireless when it was introduced just two years ago,” said Ralph de la Vega, president and CEO, AT&T Mobility & Consumer Markets. “Today’s decision was made after evaluating our customers’ expectations and use of the device compared to dozens of others we offer.”

The move puts a thorn into Apple’s side as it wrestles with whether to allow apps like Google Voice onto the iPhone. While Google Voice isn’t a VoIP app per se, its technology can be used to make cheap calls. Apple told the Federal Communications Commission that it is still “studying” Google’s app, while the search giant told the federal agency that it was flatly rejected.

VoIP applications may threaten AT&T’s more traditional revenue models as subscribers turn to the apps to make calls instead of dialing through the network. However, locking in consumers to two-year contracts and data plans may mitigate this.

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Skype, which is wrangling with its own legal issues over whether it owns the peer-to-peer technology underlying the service, applauded AT&T’s decision. The company’s president Josh Silverman said Skype has been downloaded on 10 percent of all iPhone and iPod devices.