He said the move would be in retaliation for China's decision to raise tariffs on $US50 billion in goods. Trump also has slapped tariffs on steel and aluminum imports from Canada, Mexico and European allies.
And the markets are unnerved.
As the words flew, the benchmark Shanghai Composite Index ended down 3.78%, or 114.08 points, at 2,907.82 while Hong Kong was 3.12% lower in late afternoon trade.
The drop partially reflects traders' misplaced confidence that a major trade conflict between Washington and Beijing had been averted - or at least, indefinitely postponed.
When China was locked in a dispute with South Korea a year ago, the unofficial order was given for Chinese travel agencies to halt tour groups to South Korea. And those negotiations appeared to be going well - for Beijing, anyway.
Bardole voted for Trump, and he says while the trade agreements the president rails against have actually been good for the U.S.ag industry, he also says they've been bad for other industries.
But Stateside, these developments suffered a chilly reception. "President Trump has a great relationship with President Xi" Jinping of China.
U.S. Dollar banknotes are seen in this photo illustration taken February 12, 2018.
In an official statement, Trump said that these new tariffs would be in retaliation for China threatening to impose retaliatory tariffs on USA goods in response to the last round of tariffs imposed on China by the U.S.
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"The trade relationship between the United States and China must be much more equitable", Trump said.
Baker says that if China were really determined to strike back at the United States, it would employ what he describes as the "nuclear option" of totally disregarding American companies' intellectual property rights.
The risk of "a more meaningful impact on global trade and growth have increased", said Morgan Stanley economists in a report.
President Donald Trump announced on Monday that he was considering a 10 percent tariff on $200 billion in additional imports from China.
China had offered to ramp up purchases of American goods by $70 billion to help cut its yawning trade surplus with the United States, whereas Trump had demanded a $200 billion deficit cut.
By contrast, Trump's supporters in agricultural areas are already bristling at his protectionism. It said with retaliatory tariffs imposed by American trading partners added in, the total rises to $181 billion, or 1 percent of global trade.
Given how public and bitter the confrontation has become, experts expect that both leaders will feel politically obliged to avoid any gesture that looks like surrender.
The Dow and S&P were modestly lower on Monday, having recovered from earlier lows, as gains in energy shares helped curb declines stemming from trade war concerns after China's retaliation to USA tariffs.
But after matching USA tariffs, the world's second-largest economy is starting to run out of options after importing just $129.8 billion of American imports.
Mr. Trump accused Beijing of being unwilling to resolve the dispute over complaints it steals or pressures foreign companies to hand over technology.