The much anticipated iPhone 5S release date may face limited supply due to fingerprint sensor.

The inclusion of fingerprint sensor in the rumoured iPhone 5S may limit the production of the device to four million units in the third quarter of this year.

According to Taiwanese tech blog DigiTimes, Apple may be able to build around 3 million to 4 million units of iPhone 5S in the third quarter.

Reports claimed that mass production of fingerprint sensors commenced last May by Taiwan Semiconductor Manufacturing Co., before they were packaged at Xintec. However, there was a delay "due to issues related to integration between iOS 7 and fingerprint chips."

If rumours proved to be true, it is more likely that consumers will see an iPhone 5S release date around mid or late September.

This coincides with an analyst's reports that an iPhone 5S release date will happen in late September. According to the latest note of KGI Securities analyst Ming-Chi Kuo, the rumoured iPhone 5S is facing production delays and setbacks with the inclusion of various components. Thus, a later launch of the device is expected. The analyst also stated that the iPhone 5 with plastic casing and iPad 5 will be released earlier than iPhone 5S.

The beta version of iOS 7 hinted that the new iPhones will include a fingerprint sensor as BiometricKitUI code bundle is found in the latest beta version of iOS 7. Moreover, it includes strings on how to use a fingerprint sensor on an iPhone.

iPhone 5S release date will be soon and is expected to come with A7 quad core chip; Near Field Communication; 13MP back camera; up to 128GB internal storage and longer battery life.

The cheaper iPhone will come with 4-inch screen display, a dual core processor and an 8MP back camera all housed in a cheap plastic casing. However, based on Kuo's note, the cheaper iPhone may come with iPhone 5's specs and features.

But of course, Apple still has to confirm the iPhone 5S release date as well as its specs and features.