Apple is struggling to keep up with demand for the iPhone Duo, and it cannot yet say when supply will catch up, CEO John Ternus told Reuters after the company’s earnings report. He said production is ramping up and Apple is working to get the device to customers as quickly as possible, but it cannot predict when supply and demand will balance.

Orders placed now have estimated delivery dates in January, while stores have had limited stock available for online reservations.

Ternus also addressed reports of problems with the Duo’s inner display. He said a “very small percentage” of units had been returned and that Apple is offering replacements. Last week, Apple acknowledged an issue affecting the inner display of some devices and advised customers experiencing problems to contact AppleCare.

Apple reported record revenue of $114.5 billion for its September quarter, up 12 percent from the previous year. iPhone Duo sales were not included because the device went on sale after the quarter ended.

Sources: MacRumors.