The bigger screens could be as large as 5.5 inches.
Apple is embarking on a massive production of iPhones at its China facility next month as it battles increased competition from rivals that have launched the latest smartphone models.
Details of the models are being kept under wraps but a source familiar with the matter said Apple is planning massive production of two bigger devices, with one model to have a 4.7-inch display and the other one to sport a 5.5-inch display. Current iPhone 5 model sports a 4-inch screen.
Sources further add that the new iPhones will be rounder and thinner than previous models. But the 5.5-inch model could pose production issues as it is more complicated than the smaller version, resulting in extra efforts to boost efficiency.
Both the models are expected to be available around September.
Apple is taking a beating from competitors as Samsung and HTC have already released the larger versions of smartphone models with displays as large as 5.7-inch. The tech giant is looking to reignite sales growth, with the iPhone its biggest moneyspinner.
The trend of larger-screen devices has really caught on as well, as an estimate from Forrester Research said 40% of mobile gadgets based on Android sold in 2014 in China had display sizes of more than five inches.