Speaking at Mobile World Congress, AT&T Mobility CEO Ralph de la Vega revealed the company’s plans to extend 3G coverage to more cities in the US, improve existing coverage, and incrementally ramp up data speeds to retain the title of the fastest American 3G network.

In an interview conducted at the event, de la Vega defended his company’s 3G network in comparison to rivals and described how the company worked with handset makers to improve reliability. He specifically cited Apple, noting they communicate with Apple and suggest improvements continuously, and Apple has been very receptive to their suggestions.

On its end, AT&T has now rolled out 3G service to more than 350 cities. The company is also in the middle of completing a frequency band transition from 1900MHz to 850MHz in several markets. By the end of 2009, de la Vega said, “we’ll finish the 850MHz transition in San Francisco, we’ll finish parts of New York, and then that’ll bring the best technology 3G on the best backbone to significantly improve the quality and the coverage for 3G on our network.”

We’ll see. Spotty coverage for 3G has been one of the most consistent complaints about the iPhone, so AT&T needs to step it up a bit.