Apple is eyeing up a larger screen for the next iteration of its iPhone, with four inches said to be the minimum size requirement in order to match-up to rival phones, reports DigiTimes.

Sources within the component supply chain have noted that production lines for Apple's next iPhone have begun testing, and Apple is keen on the four-inch screen.

Apple is unlikely to reveal its plans until a launch is imminent, but given that previous iPhone updates have launched in June/July we shouldn't be kept waiting much longer.

While a larger screen might sound like a no-brainer, it will alienate users who don't want a larger device bulging in their pocket.

There's also the issue of pixel density, with the Retina display on the iPhone 4 providing pin-sharp clarity. Should the screen size be increased, then Apple will also be required to up the resolution in order to maintain image quality.