US 'reciprocal' tariffs on many trading partners came into effect as the clock ticked past midnight into Wednesday in US Eastern Time, 5am in London, including a total of up to 104% on some Chinese goods.
A blanket 10% tariff on all countries kicked in over the weekend, but Donald Trump has imposed higher 'reciprocal' levies on countries he calls the "worst offenders", including economies that have large trading deficits with the US or impose their own trade barriers.
Initially, the Trump administration imposed a basic 20% tariff on China in March and a 34% 'reciprocal' measure, but after the People's Republic responded with its own 34% levy on US goods last Friday, the US President threatened on Monday that he would top this by imposing an additional 50%.
The White House confirmed on Tuesday that China's 'reciprocal' tariff would, therefore, rise to 84%, with a total tariff of 104%.
Overall US tariffs are standing at their highest level since the early 20th century.
Tariffs on other countries include 24% for Japan, 46% on Vietnam, 47% on Madagascar, 48% on Laos and 50% on Lesotho.
China said it would respond with "countermeasures" against US tariffs, while a foreign affairs spokesperson accused the US of "bullying practices".
However, various Beijing officials urged the Trump administration to resolve the dispute through "dialogue", while a white paper from the country's information office argued that trade between the countries was "roughly balanced".
Analysts at Barclays said higher tariffs on other Asian countries could also be "especially painful for China, as it will likely wreak havoc on value chains and trade diversion".
Without any fiscal stimulus, the trade shock is forecast to slow China's GDP growth to "only 2% this year, which would be the lowest growth rate since late 1970s", the analysts added.