The U.S. firm is not expected to have a 5G-enabled phone available in China until 2020, behind rivals like Huawei, Xiaomi Corp and Samsung Electronics.

There are risks integrating 5G too early into high-end smart phones because the technology requires deeply re-designing the devices with multiple new antennas. Given spotty coverage in 2019, gambling on a new design before networks are mature could be more risk than reward, said Darryn Lowe, a partner with Bain & Company. "When you think about 5G, it's a heck of a lot more complicated than an aluminum strip running around the phone," he said