China's finance ministry has announced an 84% tariff on goods imported from the US, retaliating against recent levies imposed by the White House.
The hike in tariffs, from 34%, came after US President Donald Trump's 104% tariff on Chinese goods came into force on Wednesday – they were later increased to 125%.
Trump said the 21% rise was "based on the lack of respect" China had shown, and that it would be "effective immediately".
Beijing, which has said its charges would take effect from Thursday, urged other countries to unite against Trump's tariffs as the country's exporters reel from the crippling new levies.
"Global unity can triumph over trade tyranny," declared an editorial in the state-run newspaper China Daily, noting Beijing's collaborations with Japan, South Korea and other Asian economies.
A separate piece called for the European Union to work with it to "uphold free trade and multilateralism".
The US's trade war with China continued to escalate on Wednesday. Hours after Trump's highest tariffs on a raft of countries came into force, China retaliated with its own 84% levy on US imports.
European markets dropped shortly after the announcement, with the FTSE 100 falling by 3.3% and Germany's Dax 4%.
Trump later took to his Truth Social platform to say that, in return, he was upping the US's levies on China to 125%.
"At some point, hopefully in the near future, China will realise that the days of ripping off the USA, and other Countries, is no longer sustainable or acceptable," the US president wrote.
He also announced a 90-day pause on higher tariffs for dozens of countries -except China – saying this was because those nations had not "at my strong suggestion, retaliated in any way, shape, or form against the United States".
Beijing "firmly opposes and will never accept such hegemonic and bullying practices", foreign ministry spokesperson Lin Jian told reporters on Wednesday – before the latest hike from Washington.