Rod Hall said in an investor note that while there was some improvement in the smartphone market in China during the second quarter, his forecast for third-quarter sales indicated a 15% decline year-on-year, CNBC reported.
He said while the latest iPhone models could act as a bulwark against the lessening demand, the overall decline in demand could hurt the company's bottom line.
Hall's prediction comes at about the same time as a mobile plan comparison website said that the higher prices for the new iPhone models could be stifling sales in Australia.
Hall said that his estimate of iPhone sales for the December quarter of 80 million units included 13 million from China or 16% of the total. In December 2017, China accounted for 19% of the iPhone units, while the figure was 18% for 2016.
His projections said Apple's diluted earnings per share would be US$11.78 for the current fiscal year and US$13.77 for 2019.
Apple shares decreased in value by 1.6% on Monday following Hall's note. For the year, they are up 29%.