It is highly likely that Apple (AAPL) will introduce its 2013 flagship, the iPhone 5S, before September 28 as the tech giant aims to realise its projected revenues of between $34 billion and $37 billion in the last quarter of 2013, a new report said.

The time frame makes sense, Gotta Be Mobile insists, as it is the iPhone that would push Apple's fourth quarter surge. Releasing the device a few days before Q4 starts would allow the tech giant to collect buffer sales geared for the same period, thus inching it closer to the December sales goal, the report said.

The 5S is the automatic choice for the company in which to anchor its fourth quarter sales performance since traditionally, the handset is Apple's main income generator. Looking at the June quarter results, the iPhone 5 and previous models indeed delivered the goods.

Apple tablets - the iPad Mini, the iPad 4 and older generations - also posted good numbers but actually declined in volumes sales when compared to the figures recorded in the same period in 2012.

The maximum margin guidance of 37 per cent indicated by Apple for Q4 2013 "likely indicates that the new product launch this quarter will be an iPhone and not a lower margin iPad. While new iPhones are lower margin at launch, they are still higher margin than iPad's," GBM quoted Walter Piecyk of BTIG.

Mr Piecyk contends that the company's intention of closing out the year with record sales is closely tied with an iPhone 5S roadmap that points to a late September 2013 release date, adding that the move "could be the start of a string of new product announcements," from Apple.

Apple CEO Tim Cook has implied earlier this year that his company is about to pull off surprise in last few months of the year, beginning in September, which analysts conjectured as the iPhone 5S arrival.

This week, Mr Cook echoed the same hints by declaring that there will be "amazing new products that we will introduce in the fall and across 2014."

Fun time for Apple and its million of fans, GBM said, should commence September 20 at the earliest, which should give the tech giant more than a week to implement iPhone 5S pre-orders that could snowball into a giant leap for the company's fourth quarter showing in the current year.