T-Mobile USA is latest rumored iPhone suitor

We still don't know when AT&T's exclusive contract with Apple will expire, but that doesn't stop the continued rumors of the iPhone expanding to new carriers in the United States.

Usually it's Verizon Wireless that we hear is close to signing up to service the iPhone, but a report in Cult of Mac on Wednesday says it's actually T-Mobile that "is very close to getting the iPhone in the fall."

The report quotes an anonymous "highly placed" source at T-Mobile, who says the negotiations between Apple and the carrier are in an "advanced stage" and that it's "80 percent likely" the phone will arrive on T-Mobile's network in the third quarter.

It's unclear from where the 80 percent figure is derived. We do know that at one point, Apple and AT&T had a five-year exclusive service agreement. USA Today originally reported the contract length in 2007, which would keep the iPhone away from other U.S. carriers until 2012 at the earliest. Whether that has changed is not clear, but "this fall" or "third quarter" seems a little early. AT&T did, however, suddenly allow current customers whose contracts expire anytime this year to get an early upgrade for the iPhone 4, which could be a sign that AT&T is anticipating the end of its exclusive contract.

It's pretty clear that Apple is interested in expanding its device to other carriers--it's already done so in several countries and has seen an uptick in new subscribers, according to Chief Operating Officer Tim Cook. If Apple were to pursue that strategy in the States, T-Mobile is a much more natural fit for the iPhone than Verizon, when put in proper perspective.

Both AT&T and T-Mobile use SIM cards and operate GSM networks. Verizon, on the other hand, does not use SIM cards, and it is a CDMA operator. Apple has been rumored on several occasions to be building a CDMA version of the iPhone. But on Monday, Wired reported that Apple had even spoken to Qualcomm about using its chips for such a phone--a move that would have required overhauling the design and manufacturing of the iPhone--and ultimately dropped the idea.

Besides being more realistic for the iPhone, the two companies already have a relationship: T-Mobile parent company Deutsche Telekom offers the iPhone through T-Mobile and Orange in Europe and the United Kingdom.

It's also clear that Apple and AT&T aren't trying to pretend that they have a great relationship anymore. During Apple's earnings call on Tuesday, when pressed about adding carriers, Cook had even less to say on the topic than ever.

"We are very happy to be partnering with AT&T, and they've been a first-class partner and really pioneered the smartphone growth from a network point of view in the U.S.," Cook said. "And that's all I have to say about that."

His comment on the matter was, on the whole, complimentary. But it was definitely a bit more clipped than usual. Of course, if Apple does go with another carrier, it's extremely unlikely that it would leave AT&T, so bad-mouthing the company outright doesn't make a lot of sense. Rather, Apple would likely use another carrier to augment the iPhone's current availability. T-Mobile definitely doesn't have as large a network as AT&T, specifically in rural areas of the U.S., so it would function well as a complement to the iPhone's availability on AT&T more than anything.

A new carrier, however, does not signal an automatically better experience for iPhone users in places like San Francisco and New York. It's not clear that T-Mobile (or any other carrier) wouldn't experience problems with its network similar to what AT&T has dealt with, should it start offering the iPhone. It's likely that the amount of data users Apple generates for any carrier would be overwhelming.

CNET's Kent German contributed to this report.