With no action from the Trump administration to reverse the increase, US Customs and Border Protection imposed the new 25 percent duty on affected US-bound cargoes leaving China after 12:01 a.m. EDT (0401 GMT) on Friday.
Goods in the more than 5,700 affected product categories that left Chinese ports and airports before midnight will be subject to the original 10 percent duty rate, a CBP spokeswoman said.
The grace period was not applied to three previous rounds of tariffs imposed last year on Chinese goods, which had much longer notice periods of at least three weeks before the duties took effect.
Trump gave US importers less than five days notice about his decision to increase the rate on the $200 billion category of goods to 25 percent, which now matches the rate on a prior $50 billion category of Chinese machinery and technology goods.
The hike comes in the midst of two days of talks between top US and Chinese negotiators to try to rescuing a faltering deal aimed at ending end a 10-month trade war between the world's two largest economies.
The biggest Chinese import sector affected by the rate hike is a $20 billion-plus category of internet modems, routers and other data transmission devices, followed by about $12 billion worth of printed circuit boards used in a vast array of US-made products.
Furniture, lighting products, auto parts, vacuum cleaners and building materials are also high on the list of products subject to the higher duties.
Gary Shapiro, chief executive of the Consumer Technology Association said the tariffs would be paid by American consumers and businesses, not China, as Trump has claimed.
"Our industry supports more than 18 million US jobs – but raising tariffs will be disastrous," Shapiro said in a statement. "The tariffs already in place have cost the American technology sector about $1 billion more a month since October. That can be life or death for small businesses and startups that can’t absorb the added costs."
Economists and industry consultants have said it may take three or four months for American shoppers to feel the pinch from the tariff hike but retailers will have little choice but to raise prices on a wide range of goods to cover the rising cost of imports before too long, according to economists and industry consultants.
This story has been published from a wire agency feed without modifications to the text. Only the headline has been changed.