“Starting on October 1st, the 250 BILLION DOLLARS of goods and products from China, currently being taxed at 25 percent, will be taxed at 30 percent,” Trump wrote on Twitter. “Additionally, the remaining 300 BILLION DOLLARS of goods and products from China, that was being taxed from September 1st at 10 percent, will now be taxed at 15 percent. Thank you for your attention to this matter!”.

Zhu Huani of Mizuho Bank in Singapore said what he called Trump’s “tariff tantrum” was setting off “the sense that tariffs could continue to rise,” with the “the unpredictability of timing and extent of these trade actions risk accentuating the paralysis of business decisions and big-ticket business spending.”

“No matter which way you cut the cake, it is nearly impossible to construct a bullish, or even neutral scenario for equity markets today,” said Jeffrey Halley, senior market analyst at Oanda.

Trump also said Friday morning that he was “ordering” UPS, Federal Express and Amazon to block any deliveries from China of the powerful opioid drug fentanyl. The stocks of all three companies fell as traders tried to assess the possible implications.

The president has also raged against Federal Reserve chairman Jerome Powell for his continued refusal to cut interest rates, at one point saying: “My only question is, who is our bigger enemy, Jay Powel (sic) or [China’s] Chairman Xi [Jinping]?”

That outburst came after Powell, speaking to central bankers in Jackson Hole, Wyo., gave vague assurances that the Fed “will act as appropriate” to sustain the nation’s economic expansion. While the phrasing was widely seen as meaning interest rate cuts, he offered no hint of whether or how many reductions might becoming the rest of the year.

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Some analysts, however, are confident the Federal Reserve will lower interest rates this year.

A quarter-point rate cut reduction in September is considered all but certain.

Fox News’ Ronn Blitzer, Joseph Wulfsohn, and The Associated Press contributed to this report.