Apple's otherwise solid June-quarter results were held back by a 10 percent year-over-year revenue drop in China, likely caused by the iPhone's slipping position in the local market.

"Greater China" revenues fell from $8.848 billion to $8.004 billion, according to Apple's filings with the U.S. Securities and Exchange Commission. The company was also down from $10.726 billion in Q2 2017, but the June quarter is typically a slow period as few products are launched and many shoppers wait for new iPhones in the fall.

Apple is just barely holding on to fifth place in the Chinese smartphone market, according to Canalys estimates. The top four spots are held by local Android-based brands Huawei, Oppo, Vivo, and Xiaomi.

The main issue is likely price, since Apple doesn't offer any low- to mid-range phones apart from older models. Its competition being local and Android-based may offer a further cost advantage, even though many Apple supply and assembly partners are based in the country.