It has only been a week since the iPhone 6s has been unveiled in the much-anticipated Apple event on Sept 9, Wednesday. But it appears that the latest iPhone from the Cupertino tech giant has been met by overwhelming demand as the U.S. started pre-orders for the device on Sept 12. Apple is trying to keep up with the fast-rising demands, especially for the bigger handset, the iPhone 6S Plus.

According to NDTV Gadgets, many retailers in the U.S. are still apt on promising a Sept 25 arrival of the iPhone 6s shipments. Despite the promise, the increasing number of pre-orders is already indicative of a 3-4 week delay in shipping schedule. But apart from the high demand for the new handset, recent reports suggest that Apple may be having problems with the smartphones' backlights.

A CNET report said that the company which makes backlights for the iPhone 6s, Japanese firm Minebea, has been suffering from production issues. This is according to analyst Ming Chi Kuo of KGI Securities. Ming Chi Kuo said in a note that Apple may be transferring some orders to Radiant, another supplier for the neccessary part. The company will then be seeing orders increase by 70 to 80 percent within the month.

"To accelerate availability, we believe Apple has been transferring substantial 6s Plus backlight module orders to Radiant," the note said. "As such, we estimate the company's iPhone 6s Plus backlight module orders to increase by 70-80 percent to 4-5mn units in September," the note further indicated that the allocation will be increasing to 70 to 80 percent in the month. 

Apple has claimed that the new iPhones are "very strong around the world." Online demands have also been great for the new products. The iPhone 6s sales are expected to get a boost from China, as the country  has been included in the launch. Analyst Gene Munster said that CChina is likely to account for 2 million units worth of iPhone 6s for Apple's opening weekend.