Apple is planning to rollout the rumoured phablet-size iPhone 6 a bit earlier than projected, likely causing delays on the iPhone 5S production and bringing pressure on the latter's Q4 2013 inventory, a new report said.

In a new research note released Friday last week, Citi Research analyst Glenn Yeung reported that production activities for the 2013 Apple flagship have encountered delays by two weeks.

While the glitch will not pushback the iPhone 5S' September release date, "we suspect (iPhone 5S) volumes in September may consequently be challenged," CNET reported Mr Yeung as saying in the note.

The assessment, the analyst noted, was based on "our field work in the hardware supply chain."

Such slight distraction, however, would not prevent Apple from accelerating efforts to finally match Samsung's relatively unchallenged rule of the global phablet market, Mr Yeung said.

By the first quarter of 2014, "we expect a 4.8-inch screen iPhone 6 to be launched," the analyst added, creating the possibility that Apple will let loose the large-screen iOS 7 smartphone a few months after the rumoured September unpacking of the 5.99-inch Galaxy Note 3.

The Citi report also pointed to a barrage of product surprises from the tech giant, as earlier hinted by Apple CEO Tim Cook.

Among them are two new iPad Mini versions - a cheaper iPad Mini edition that Mr Yeung said will retail for as low as $US230 and the much-awaited iPad Mini 2 with Retina, flashing a stunning resolution of 2048 x 1536.

The latter's arrival, however, will have to wait until late 2013, the report said, giving the impression that Apple encountered numerous production issues for its next-generation iOS devices.

As for the 9.7-inch iPad 5, "we continue to expect iPad 5 to sport characteristics similar to iPad Mini (slimmer, lighter)," Mr Yeung said.

The release of these new iPad makes, he added, will end the iPad 2 and iPad 4 lifecycle, which the note said will be continued after Q3 2013.