There may not be enough units to meet the expected surge of demands for the iPhone 5S shortly after its rumoured September release date as one report claims that Apple will limit the iOS 7 device production for the second half of 2013.

From the earlier forecast of 120 million units at the maximum, Apple's Chinese iPhone manufacturers were reportedly instructed to downgrade the target output to 100 million, tops, or a reduction of some 20 per cent, Brian Blair of Wedge Partners told CNBC in an interview this week.

The production guidance will be in effect starting Q3 2013 and will last to the end of the current calendar year, Mr Blair said, adding that the information came "from some of our supply-chain work out of China and Taiwan."

It is understood too that Apple's supply chain players, at least those directly involved in producing the iPhone 5S and its predecessor the iPhone 5, have been informed of the major adjustment, advising them of the impending cut backs in components orders for the remaining months of 2013.

The move, according to Mr Blair, was one of the measures being implemented by Apple to mitigate the impact of the perceived slow down in the global smartphone market, highlighted recently by the earnings guidance released by Samsung that slightly missed previous projections.

His note somehow echoes earlier concerns voiced out by analysts - that the iPhone 5S rollout could run into short-term distribution issues as Apple grapples with a mix of production challenges and prevailing market sentiments.

While it appears that the upscale mobile phone market is reaching a saturation point, Apple is given more reason to enter the low-cost segment, which Mr Blair said will surely happen in the few months ahead via the rumoured budget iPhone, now known as the iPhone Lite.

This cheaper iPhone is essentially a version of the soon-to-be retired iPhone 4, only with a plastic back cover and inner parts that according to Mr Blair have been sitting on Apple's inventory in the past four years.

By combining affordable materials and existing component stocks, Apple could afford to come up with the iPhone Lite while putting a lid on its second half production numbers for 2013, the analyst explained.

More so, the tech giant would have enough room to give the iPhone Lite an attractive price mark and maintain a healthy profit margin at the same time, Mr Blair said. Analysts believe the Lite will sell between $300 and $400.

Release date for both the iPhone 5S and the iPhone Lite is pegged on September, with the commercial availability to follow in the immediate weeks ahead or first week of October at the earliest.