Apple may not sell it's larger iPhone 6 with 5.5-inch display, also called iPhone Air, until 2015.

Apple may, for the first time, unveil two iPhones when it announces the iPhone 6 around September. This is what the rumour mill has been saying, from many different sources, for months.

Now a report from KGI Securities analyst Ming-Chi Kuo says Apple won't be putting its larger iPhone Air on sale until 2015.

The iPhone 6 model that will first arrive, at 4.7-inches, has apparently been suffering production issues associated with the larger screen size. These issues will become even more complicated for the larger 5.5-inch model, according to Kuo.

Kuo says: "Production bottlenecks on 4.7-inch iPhone 6 centre on the yield rate of in-cell touch panel and metal casing. As in-cell touch panel becomes larger in size, the edge of the panel may become insensitive to touch. Meanwhile, under new manufacturing process for the iPhone 6 metal casing, colour unevenness is an issue."

According to Kuo Apple will also be dropping its prices for the iPhone 5S and 5C.

Apple is expected to release the iPhone 6 in September with a sapphire glass screen, new A9 processor, improved camera and thinner profile.

READ: iPhone 6 with 4.7-inch screen tipped for early release, 5.5-inch version to follow