Its forecast for the iPhones with 4.7-inch (11.9-cm) and 5.5-inch (14-cm) displays is much larger than the initial order last year of between 50 million and 60 million for iPhone 5S and 5C models, the people told the Journal.

Foxconn and Pegatron Corp plan to start mass producing the 4.7-inch iPhone model next month, and Hon Hai Precision Industry Co Ltd, whose parent is Foxconn, will begin making the 5.5-inch version exclusively in September, the people said.

Both iPhone 6 screens will be larger than the 4.0-inch (10.2-cm) panels on Apple's existing iPhone 5S and 5C models.

The new phone models are also expected to feature metal cases similar to the iPhone 5S and likely come in multiple colors, the people said.

Both iPhone 6 screens are expected to use in-cell touch panel technology, built into the screen and allowing for thinner construction than with standard touch panel films, that was introduced with the iPhone 5, sources said in March.

There could be difficulties with in-cell production technology for the larger 5.5-inch size, one of the sources said then.

To factor in the possibility of a higher failure rate for displays, Apple has asked component makers to be prepared to make up to 120 million iPhones, the people told the Journal on Monday.