On Friday morning, the S&P 500 was less than a couple of points from another all-time high. Then, after a single social media post from President Donald Trump , $2 trillion in market value was wiped out.

The unraveling shows the sway the president's one-man trade policy still has over the fate of the global economy.

Trump at 10:57 a.m. ET wrote on his Truth Social platform that China was "becoming very hostile" with the rest of the world, especially when it comes to its control of rare earth metals. He accused China of holding the world "captive" because of its "monopoly" on these crucial resources.

The key part that the stock market reacted to in the 500-word Trump post was this: "One of the policies that we are calculating at this moment is a massive increase of tariffs

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