Fourth-ranked US wireless carrier T-Mobile has announced a new partnership with Apple, which should allow it to begin offering the iPhone on its network sometime next year.

The company dropped the bombshell in a notice to investors on Thursday, saying only, "T-Mobile USA has entered into an agreement with Apple to bring products to market together in 2013."

While that terse statement stopped short of mentioning the iPhone specifically, it seems unlikely that sales of iPads through carriers are strong enough for T-Mobile to sign a tablet-only deal.

Whether that means T-Mobile will offer the iPhone 5, earlier models such as the iPhone 4S, or an as-yet-unannounced model remains unknown.

Of the four leading US carriers, only T-Mobile does not currently sell Apple's überpopular smartphones. Apple launched the original iPhone as an AT&T exclusive in 2007, but in 2011 it broadened its market to include Sprint and Verizon.

Even some smaller players now carry iPhones, such as Cricket and C Spire Wireless, which puts T-Mobile at something of a disadvantage, given that US customers still plonk down for Apple smartphones more than any other brand.

Not that T-Mobile hasn't tried to cater to fanbois. In October, the carrier began stocking iPhone 5–compatible NanoSIM cards – despite the fact that none of the phones T-Mobile sells use them – in hopes that customers would find its new unlimited data plans attractive enough to bring their unlocked iPhones to its network.

The company has even gone as far as to display iPhones in its retail stores – not to sell, mind you, but merely to demonstrate how well T-Mobile's data service works with Apple phones purchased elsewhere.

T-Mobile hasn't released any figures to indicate how well these efforts have worked, but common sense suggests it's still more convenient for customers to buy an iPhone with a bundled service plan from AT&T, Sprint, or Verizon than to buy an unlocked version and activate it with T-Mobile.

That will change if T-Mobile begins offering iPhones next year, which could give a belated but much-needed boost to the carrier's subscriber base.

Although T-Mobile is considered one of the top US carriers, it has struggled to compete with market giants AT&T and Verizon. T-Mobile's recently announced merger with MetroPCS is expected to give it a total subscriber base of about 42 million customers, but each of the two leaders boasts more than twice that number.

Joining the iPhone party could go a long way toward helping T-Mobile narrow that gap. In AT&T's most recent financial results, it announced that it sold 6.1 million smartphones in the third quarter of 2012. Of those, 4.7 million – 77 per cent – were iPhones. ®