WASHINGTON (Reuters) - 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.

FILE PHOTO: Containers are seen at the Yangshan Deep Water Port, part of the Shanghai Free Trade Zone, in Shanghai, China March 14, 2018. REUTERS/Aly Song

The further tariffs were being considered “in light of China’s unfair retaliation” against earlier U.S. trade actions, which included a proposed $50 billion of tariffs on Chinese goods, Trump said in a White House statement.

Financial markets, unsettled for days by the trade fight and Trump’s management of it, whipsawed again on the new threat. After a bullish regular trading day, U.S. equity futures sold off sharply in after-market-hours trading.

S&P 500 e-mini futures traded down 1.3 percent EScv1, with similar moves in Dow and Nasdaq futures 1YMcv1 NQcv1. In the currency markets, the U.S. dollar fell against the Japanese yen.

“The hastily crafted policy like we have seen from Trump over the last two, three days and now tonight ... is dangerous,” said Doug Kass, who runs hedge fund Seabreeze Partners Management Inc. “Our president is going to make market volatility and economic uncertainty great again.”

In his statement, Trump said the U.S. Trade Representative had determined that China “has repeatedly engaged in practices to unfairly obtain America’s intellectual property.”

Earlier this week, the Trump administration proposed 25 percent tariffs on 1,300 Chinese industrial and other products. China shot back with a list of similar proposed duties on American imports, including soybeans, planes, cars, beef and chemicals.

    “Rather than remedy its misconduct, China has chosen to harm our farmers and manufacturers,” the Republican president said.

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