Virgin Mobile USA, the prepaid brand owned by US number-three operator Sprint, is to begin offering the iPhone later this month, marking the second deal Apple has struck with a prepaid carrier in as many weeks.

Virgin Mobile will offer the iPhone 4 and iPhone 4S beginning 29 June, offering unlimited data and messaging plans from as low as US$30 per month without a contract. Customers can also use the device as a mobile hotspot for an additional US$15 per month.

The base tariffs are lower than the iPhone prices unveiled by rival prepaid operator Leap Wireless last week, which will offer a US$55 per-month, all-inclusive unlimited talk, text and data iPhone plan when it launches the device via its Cricket brand on 22 June.

However, Virgin Mobile’s up-front costs for the devices are higher, charging US$549 for the 8GB iPhone 4 and US$649 for the 16GB iPhone 4S, compared to US$399 and US$499 at Cricket.

Sprint already offers the iPhone to its postpaid customers and analysts believe the Virgin Mobile prepaid deal may see it lure more iPhone customers away from larger rivals AT&T and Verizon Wireless.

“At US$50 per month (versus comparable unlimited options from AT&T at US$100-plus per month), we believe this could gain some traction among U.S. customers who are able to pay the upfront costs,” Brian Marshall, an analyst at ISI Group, told Bloomberg.