The customs document said the move was in accordance with an executive order made by Trump last month, “due to the determination that Hong Kong is no longer sufficiently autonomous to justify differential treatment in relation to China”.
A 45-day grace period would be granted to importers following the announcement to allow them time to ensure no goods were marked “Made in Hong Kong”, it added.
Trump’s order, signed on July 14, also ends preferential treatment for Hong Kong passports, revokes license exceptions for certain exports, suspends Washington’s extradition agreement with the city and stops any joint police training.
The United States last week imposed sanctions on a group of Chinese and Hong Kong officials — including city leader Carrie Lam — in response to the crackdown.
China condemned the sanctions as “barbarous” and imposed retaliatory sanctions on some senior American politicians and leading human rights campaigners.