Cricket won't be the only US carrier in 2012 to offer the iPhone with a prepaid plan. According to sources speaking to MarketWatch, Sprint plans to begin offering prepaid versions of the iPhone through Virgin Mobile in the US—a carrier that contracts with Sprint to make use of its network. The announcement is expected to come sometime this week, and the phones will reportedly be available as soon as July 1.

As MarketWatch notes, Virgin Mobile USA's prepaid plans currently start at $35 per month with unlimited data (the carrier begins throttling data speeds once the account crosses the 2.5GB mark in a month). That, however, doesn't necessarily mean the plans offered with the iPhone will cost that little; it seems plausible that Virgin Mobile will charge more for the iPhone because of the heavy data usage that tends to come with it.

By comparison, Cricket's iPhone plans will cost $55 per month with unlimited calls, texts, and data, so we wouldn't be surprised to see Virgin Mobile's plans end up being somewhat similar to what Cricket offers. And since Sprint's network is much more widely available than Cricket's (contracted through Leap Wireless), more US customers will be able to take advantage of the Virgin Mobile offering once it goes public.

MarketWatch didn't have any further details on which devices would be offered through Virgin Mobile or how much the company planned to charge for them. If the announcement is indeed coming down the line this week, however, we'll soon be able to make a more direct comparison between Cricket's and Virgin Mobile's iPhone offerings. Meanwhile, T-Mobile USA remains out in the cold without an iPhone to call its own—people who own GSM iPhones through AT&T have begun having theirs unlocked and switching over to T-Mobile, but without an iPhone that works on all of T-Mobile's GSM bands, the national carrier is now falling behind even tiny regional carriers when it comes to device selection.