"We are not in a trade war with China, that war was lost many years ago by the foolish, or incompetent, people who represented the US," Trump said in a morning tweet.
"Now we have a Trade Deficit of $500 Billion a year, with Intellectual Property Theft of another $300 Billion. We cannot let this continue!"
The Chinese action was, in turn, in response to the Trump administration's own $50-billion list of Chinese products that face US tariffs over Beijing's alleged theft of intellectual property and technology.
The last month has seen the mercurial Republican leader rattle markets in announcing punishing new tariffs on exports from major trading partners, against warnings from industry groups and members of his own party. (AFP)