Apple said it is working hard to get the iPhone Duo into customers' hands as quickly as possible. (EPA Images pic)SAN FRANCISCO: Apple on Wednesday said it will have 'limited' numbers of its folding iPhone Duo phone available for walk-in customers when the device launches Friday, after initial online orders sold out in minutes and pushed delivery times for some customers to January.

Apple announced its first folding phone in September, with analysts expecting it to quickly come to dominate a niche segment where rivals such as Samsung Electronics and Huawei Technologies have sold premium offerings for years.

However, the iPhone Duo is also a more complex product than standard candy-bar iPhones, with a tight-fitting hinge that analysts believe may take time for Apple to learn to manufacture in high volumes.