The rumoured 4.8in iPhone, peculiarly dubbed 'iPhone math', is in the works at Apple, but won't launch in 2013, according to a new report.

Earlier this week, a report from China Times sparked speculation about the so-called 'iPhone math', which sources claimed would launch later this year alongside two additional iPhones expected to be the iPhone 6/5S and an iPhone with a 12-megapixel camera.

But now, Taiwan-based tech site Digitimes cites 'industry sources' who say that Apple won't be launching a bigger iPhone in 2013.

Digitimes highlights speculation that Apple will launch an iPhone with a 4.8in this year, but says that its sources claim the rumour is only half true. "Apple is indeed developing an iPhone with a bigger screen, but that will not be among the models to be launched this year," reads the report.

According to Digitimes, Apple will launch two new iPhones in 2013, both of which are likely to have a 4in display and the in-cell technology that is currently used in the iPhone 5's touchscreen. Previous reports suggested that Apple could move away from the in-cell display in its next iPhone due to interference issues experienced by many iPhone 5 users since its launch.

The report suggests that one of the two new iPhones is likely to be a lower-cost model, but sources have noted that Apple could struggle will low supplies of the in-cell displays due to mass production issues last year.

Digitimes expects that iPhone shipments will reach about 37 million units in the first quarter of 2013, with 20 million of those likely to be the iPhone 5. However, iPhone 5 shipments could fall to about 18 million units in the second quarter of the year, says the report.

This week's reports are not the first to speculate about a possible bigger iPhone that could compete with the emerging 'phablet' market, which includes Samsung's Galaxy Note.

Earlier this month, Topeka Capitals analyst Brian White said that the next iPhone could come in three sizes, including a smaller and larger model, and last year, Jefferies analyst Peter Misek said that a 4.8in iPhone was among several iPhone 6 prototypes "floating around".

Following Digitimes' new report, Misek sent a note to investors reiterating his predictions.

"We believe a lower-cost 4.3in iPhone and multicolour 4in iPhone 5S will launch in June/July," the note reads. "Additionally, we believe a 4.8in iPhone model is scheduled for the end of October. We do not know what this phone will be called and think 'Math' might be a mistranslation or a code name."

See also:

Predictions: What Apple will release in 2013

iPhone 6 release date, rumours and leaked images

New thinner and more power efficient iPad 5 could feature 'stunning' screen

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