By Chris Smith

Published: 04:47 PM EST (01:47 PM PST)

Apple is expected to start selling the iPhone 5 simultaneously with three of the Big Four mobile operators in the USA, Sprint being reported to join AT&T and Verizon for a mid-October launch.

According to a report by the Wall Street Journal, Sprint, the number 3 carrier in the US, will start selling the fifth-generation iPhone this fall, giving Apple access to an important new channel for selling its iconic device in America. Sprint currently has just over 52 million subscribers compared to Verizon’s 106 million and AT&T’s 99 million.

Since the launch of the first iPhone in 2007, Apple has slowly shifted its policy regarding its carrier partners both nationally and internationally, replacing exclusive iPhone carrier deals with partnerships with multiple mobile operators in various markets around the world.

America was the last market to lose carrier exclusivity. In the US, the iPhone was originally available only from AT&T until Verizon started selling a CDMA version of the iPhone 4 in February of this year. Rumors have suggested that Sprint and T-Mobile would be next in line to carry the iPhone, with a recent job posting revealing Apple’s specific interest in a future collaboration with Sprint.

Like Verizon, Sprint would require a CDMA version of iPhone 5, although a number of reports have provided evidence that Apple’s next-gen smartphone will come with “World Phone” capabilities. A dual-mode GSM/CDMA iPhone 5 running iOS 5 has already been noticed in app usage logs by developers, for instance. Sprint is also said to begin carrying a CDMA iPhone 4 starting with the same date.

Richard Doherty, the director of research firm Envisioneering Group, believes that Sprint needs the iPhone in order to prevent its customers interested in the iOS smartphone from changing carriers in order to buy the device.

In the quarter ending in June, Sprint has posted a loss of subscribers on comparison with its main rivals, AT&T and Verizon, which gained more customers partly due to their strong iPhone sales. However the addition of the iPhone to Sprint’s lineup will not have any impact on the company’s fiscal fourth quarter ending in September.

AT&T sold 7.2 million iPhones in the first half of the year, including iPhone 3GS sales, a device still carried by the GSM mobile operator while Verizon sold 4.5 million iPhone 4 units in the same period of time. Peter Oppenheimer, Apple’s chief financial officer, noted during the last earnings call that “a future product transition that we are not going to talk about today” would occur the company’s September quarter.

Recent disclosures suggest Apple will introduce a cheaper 8GB iPhone 4, in addition to an all-new, fifth-generation model dubbed either the iPhone 4S or iPhone 5, in September and that the company is currently working on ad spots for the new handsets that will be finished in early October, suggesting general availability of both models during the first or second week of October.