Foxconn chairman Terry Gou has said that his factories are struggling to meeting demand for Apple's iPhone 5.
Chinese firm Foxconn is Apple's primary manufacturer of iPhones and has recently faced increased pressure to manufacturer the reportedly hard to build new iPhone.
"It's not easy to make the iPhones," Gou was quoted as saying by Reuters.
"We are falling short of meeting the huge demand."
Foxconn has recently come under increased pressure to improve working conditions and meet growing product demand.
Apple took a tour of the manufacturer's factories to access conditions last August. Company chief executive Tim Cook came away from the tours feeling positive that working conditions were improving.
However, Foxconn came under fire soon after the visit when a 2,000 worker riot led to a single day work stoppage. Some workers group blamed the intensive manufacturing process involved in building iPhone 5s for stoking tensions at the plant.
The high demand and complicated process involved in making the new iPhones heightened already tense working conditions, according to Chinese workers' rights group Chinese Labor Watch (CLW).
It was also recently reported that the strenuous iPhone 5 production led to a short workers strike. According to CLW, workers attempted a short lived strike on the grounds that they were improperly trained and couldn't keep up with the iPhone's increased quality demand standards.
Apple's difficulties in its supply chain haven't stopped it from profiting off of its new iPhone. The firm's fifth iteration of the iPhone sold over five million copies.