Numerous sectors, from oil to automobiles to banks and railroads, were reeling from Trump's threat to impose a 5 per cent tariff starting June 10 on the US$348 billion ($532.5b) in goods that the US imports from Mexico. Trump's threat follows his frustration over Mexico's apparent inability to slow or stop the flow of illegal immigration crossing the Mexican border and entering the US.
Automobile stocks were among the hardest hit because they are the most vulnerable to tariffs on Mexico-built products, with Ford, General Motors and Fiat Chrysler trading down 2.26 per cent, 4.25 per cent and 5.82 per cent respectively. Verizon, Cisco and Dow Chemical were the biggest drags on the blue chips, with 29 out of the 30 stocks losing ground. Only McDonald's showed a gain. Nine of 11 US S&P sectors were down, with only utilities and real estate staying out of the red.
"This is very concerning, " said Kristina Hooper, chief global market strategist at Invesco. "This is a new and unexpected frontier in that tariffs are being used as a weapon beyond just trade policy. Markets don't like surprises and this is a big surprise."
Losses were broad and deep as the month closed. Financial stocks were also hit hard. JPMorgan Chase, Goldman Sachs, Bank of American and Wells Fargo were down in the early afternoon. Shares in Kansas City Southern, a railroad network that carries freight between the US and Mexico, fell 4.5 per cent. Union Pacific, which derives 5 per cent of its revenue from goods coming in from Mexico, dropped 1.59 per cent.
Commodities were moving. Gold prices increased 1.46 per cent to US$1,305.90 an ounce as money gravitated to safety. Copper prices, a predictor of economic activity, fell.
Oil prices fell sharply on fears that a slowdown could reduce global consumption. West Texas Intermediate and Brent crude, both bellwethers, crashed more than 5 per cent. US oil was selling at US$53.50 per barrel. Mexico is also one of the biggest suppliers of oil to the US, selling more than 22 million barrels to its northern neighbor in March, according to the US Energy Information Administration.
Asian markets were in decline across the board. Japan's Nikkei 225 tumbled 1.6 per cent, the Hong Kong Hang Seng fell 0.80 per cent and the Shanghai Composite was down a quarter per cent. The Chinese stocks were hit by disappointing data from the country's manufacturing sector.
The German DAX was leading a uniform downturn on European markets with a 1.47 per cent decline.
The closely watched yield on 10-year Treasury notes was sailing into a two-year low, at 2.176 per cent, as worried investors headed for the safety of bonds. Yields drop when bond prices rise, and prices are rising for US Treasurys.
"Expect the 10-year Treasury yield, which is a more accurate gauge of fear than the Volatility Index, to move lower as investors turn decidedly 'risk off' in the face of this alarming decision," Hooper said.
The trade war has detoured what had been one of the strongest stock market starts in years, thanks to a strong US economy and better-than-expected corporate earnings.
But back and forth economic threats between the United States and China increased in May, erasing stock gains and creating economic uncertainty in the US and among its trading partners.
"If you are a corporate planner, what the heck are you going to do?" said Howard Silverblatt of S&P Dow Jones Indices. "The level of uncertainty has significantly increased. That prevents commitment in corporate America."
Recession worries are growing, and investors are betting the Federal Reserve will come to the rescue later this year with multiple rate cuts.
Global interest rates declined, with the German 10-year bond yield trading at the historic low of negative 0.21 per cent. The markets are now pricing in the likelihood of an interest rate reduction at 70 per cent for September and 90 per cent for December, according Silverblatt.
"The market was already concerned with slowing economic growth, then this trade war mishmash has raised those worries a couple of notches," said Michael DePalma, managing director at MacKay Shields.
"What you are seeing in the bond market is worry that more tariffs will pressure consumer spending and corporate profits. Investors are going to Treasury bonds to get ahead of the Fed and put their money in a safer place than stocks or corporate bonds. Riskier assets are going to be adversely affected."
Sam Stovall, chief investment strategist at CFRA, said markets have begun recalibrating to price in the long-term impact of trade wars.
"Using trade as a lever to pry whatever concessions the president desires from global trading partners is driving this market down," Stovall said.