For the world's two largest economies, the price tag would be around 1% of GDP growth, said Oxford Economics, worth about $154bn to the U.S. and $132bn to China.
President Donald Trump said on Thursday he had instructed U.S. trade officials to consider $100 billion in additional tariffs against China, upping the ante in an already high-stakes trade confrontation between the world's two biggest economies.
Earlier this month, China announced tariffs on $3bn of U.S. goods such as pork and wine in retaliation for the steel and aluminium tariffs imposed last month by Trump.
But for someone who has long fashioned himself as a master negotiator, Trump left it unclear whether he was bluffing or willing to enter a protracted trade war pitting the world's two biggest economies against each other, with steep consequences for consumers, businesses and an already shaken stock market. But they had calmed down Wednesday and Thursday on hopes the United States and China would find a diplomatic solution.
President Trump called China's retaliation against US tariffs "unfair" on Thursday, saying he was considering another wave of tariffs on Chinese goods.
"Rather than remedy its misconduct, China has chosen to harm our farmers and manufacturers", Trump said.
The escalating tariffs are raising concerns especially in the USA agricultural sector, after China announced this week it intends to hit soybeans and other farm products imported from America. That followed an announcement earlier this year that the USA would impose import taxes on aluminium and steel, which would include China. Also on the list were American beef, whiskey, passenger vehicles and industrial chemicals. "We will take new comprehensive measures to respond and resolutely defend the interests of the country and the people".
Treasury Secretary Steven Mnuchin told CNBC that the USA and China are "not actually not in a trade war" but may be in the beginning of one.
His threat followed China's threat to retaliate if the US moved ahead with its initial Section 301 moves.
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The other, "Rise Up" celebrated Nelson Mandela's presidency. "And he shed tears to say that we have made a decision to separate". Thus some of the warm tributes that have been paid following her death aged 81 ring more than a little hollow.
Financial markets, unsettled for days by the trade fight and Trump's management of it, whipsawed again on the new threat.
Kudlow said there may be more serious negotiations between the two superpowers in the coming months, and that the United States wants China to stop violating U.S. intellectual property and open the Asian nation's markets to more American merchandise and investment.
China said it was not afraid of a trade war, even though it did not seek one, and accused the U.S. of provoking the conflict.
Among sectors most affected by a trade war could be technology, particularly chipmakers. "The WTO is unfair to US", Trump said in a Twitter message.
No formal negotiating sessions have been set, the official said.
Trump delivered a similar sentiment, calling for trade barriers between the United States and China to be taken down.
"If the USA says that it will pay any price, it must be firmly attacked", China's official Xinhua news agency said on Saturday.
Trump tweeted moments later, criticizing the World Trade Organization and suggesting it's "unfair" to the U.S. Both Treasury Secretary Steve Mnuchin and Trump economic adviser Larry Kudlow were on television to promote the idea of talks, with Mnuchin telling CNBC "we are in communication regularly".
He said that any additional tariffs first would be subject to a 60-day public comment period, as would the penalties announced earlier in the week.