President Donald Trump sought late Thursday to identify an additional $100 billion in tariffs on Chinese goods, after both countries proposed $50 billion in taxes on imports from the other in an escalating trade skirmish.

The White House said in a statement after markets closed Thursday that Trump has asked the United States Trade Representative to identify another $100 billion in potential tariffs on Chinese goods. Stock-index futures fell in response, with S&P 500 futures ESM8, -1.24% , Dow Jones Industrial Average futures YMM8, -1.51% and Nasdaq-100 futures NQM8, -1.31% all signalling declines of more than 1%.

The latest move is a continuation of a growing trade dispute between the two countries. Trump previously announced $50 billion in proposed tariffs on goods imported from China, which responded by announcing about $50 billion in proposed tariffs on U.S. goods. China has also complained to the World Trade Organization about the U.S. tariffs.

In his statement Thursday, Trump again cited China’s “illicit trade practices” for the tariffs, claiming that they had destroyed American factories and jobs. He called China’s proposed tariffs “unfair retaliation” to his own, and asked the USTR to identify products that could raise another $100 billion in tariffs.

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Trump has faced pushback from U.S. business interests since China announced its proposed tariffs, especially from farmers, who would have trouble selling their wares in China. He noted in his statement Thursday that he was also seeking an approach that would help farmers who could be harmed by the levies.

“I have also instructed the Secretary of Agriculture, with the support of other members of my Cabinet, to use his broad authority to implement a plan to protect our farmers and agricultural interests,” the statement read.

Futures fall as Trump seeks $100 billion in additional China tariffs