American tech companies are getting the go-ahead to resume business with Chinese smartphone giant Huawei Technologies Co., but it may be too late: It is now building smartphones without U.S. chips.

Huawei’s latest phone, which it unveiled in September — the Mate 30 with a curved display, telephone and wide-angle cameras that competes with Apple Inc.’s AAPL, +3.75% iPhone 11 — contained no U.S. parts, according to an analysis by UBS and Fomalhaut Techno Solutions, a Japanese technology lab that took the device apart to inspect its insides.