Some big names have lent their weight to a rumour that the screen on Apple's next iPhone will measure at least 4 inches diagonally, compared to the current 3.5 inches.

Both Reuters and the Wall Street Journal have published reports today saying Apple has begun placing orders for the larger screens from its OEM suppliers.

The publications, neither known for printing rumours or gossip, both cite sources familiar with the matter.

Apple hasn't changed the size of the screen on the iPhone since the device was first introduced in 2007.

However, new devices such as the Samsung Galaxy S III (4.8 inches), the HTC One X (4.7 inches) and the crossover Samsung Galaxy Note (5.3 inches) have reset the amount of viewing area consumers expect from their smartphones.

Reuters says an increase from 3.5 inches to 4 inches would equate to a roughly 30% increase in viewing area, provided Apple doesn't change the proportions of the device.

The Wall Street Journal has also backed the rumour that Apple is testing iPad models with screens smaller than the current 9.7 inches.

The most recent iPhone, the iPhone 4S, was released in October, and as the name indicates had few significant changes from the iPhone 4. Apple has traditionally released a new iPhone once a year, leading to frequent speculation about what features the next model may include.

It's unlike Apple to toe the line set by competitors - can you see the company releasing a larger iPhone?