Apple reportedly plans to reelase a new iPhone model sometime after the summer, which will feature a larger screen as sources from display suppliers in South Korea and Japan said. According to Reuter's sources, the new iPhone screens will measure 4 inches from corner to corner. Apple has used a 3.5-inch screen since introducing the iPhone in 2007.

The reports says that production of the new screens has begun at LG Display, Sharp and Japan Display.

Apple's main competitor in the smartphone market, Samsung Electronics, has already unveiled its top-of-the line Galaxy SIII smartphone with a 4.8-inch touch-screen and a faster processor earlier this month.

Samsung has become the world's largest cell phone maker, sales boosted by the succesful launch of the Galaxy S III model.

Apple has not commented on the report. A

report in March by a South Korea newspaper said Apple would use a "retina" display on the next iPhone, the same technology in its latest iPad.