By Sam Oliver

Published: 09:30 AM EST

AT&T made a surprising announcement this week when it declared voice over IP applications could run on its 3G data network. However, the wireless carrier still is not prepared to offer iPhone data tethering.

In an unexpected reversal, AT&T revealed this week that VoIP services, like Skype, would be allowed on its wireless data network. Previously, such applications were only allowed on the iPhone via Wi-Fi.

AT&T had an agreement in place with Apple to prevent such applications from being allowed on its network for bandwidth concerns -- the same reason multimedia messaging and tethering for the iPhone were delayed.

After the launch of MMS for the iPhone 3G and iPhone 3GS in September, AT&T officials said that tethering would come at a later, unspecified date. Originally, both services were due to launch over the summer.

"By its nature, this function could exponentially increase traffic on the network, and we need to ensure that some of our current upgrades are in place before we can deliver the expanded functionality with the excellent performance that customers expect," AT&T said when MMS debuted.

The Wall Street Journal reported Thursday that AT&T still has not provided any further details on tethering, despite its acceptance of VoIP on its 3G network, as well as the launch of MMS.

"A spokesman for the wireless carrier, however, said that tethering remains unavailable," the report said, "and stuck with the company's prior statement: 'Whenever we offer new features, we want to offer the best possible customer experience. For tethering, we need to do some additional fine tuning to our systems and networks so that we do deliver a great experience.'"

The report noted that Ralph de la Vega, the head of AT&T's wireless unit, previously said that the service is expected to launch sometime in 2009. However, officials have not since repeated that information.