T-Mobile USA, the fourth-largest U.S. carrier and the only one that has yet to roll out 3G, said at Mobile World Congress that it will start turning on the faster network by summer, according to CNET’s (NSDQ: CNET) Crave.

SEE ALSO: AT&T Announces 3G Expansion And Begins Discussion Of 4G

The carrier was still vague, but at a press conference, T-Mobile International CEO Hamid Akhavan promised it would happen by this summer. Akhavan explained that the launch has been delayed because of some spectrum issues. In 2006, T-Mobile spent $4.2 billion to more than double the amount of spectrum it had in its top 100 U.S. cities. Commercial availability was supposed to come halfway through 2007, and most markets were to be live by 2008.

Akhavan assured the crowd that the issues have been resolved and that the carrier is putting together a “robust” network that will be the best 3G network in the U.S. Still, last we heard, T-Mobile was building out its markets with UMTS, not the faster HSDPA that AT&T (NYSE: T) has already started to deploy.

During the same press conference, Akhavan confirmed T-Mobile would be Apple’s official iPhone launch partner in Austria, and start offering the device during the first half of the year, according to Macworld.