Just when it seemed as if the United States and China were quietly making progress toward reaching a trade deal, President Donald Trump fired off a Sunday morning tweet threatening to ratchet up tariffs on Chinese imports because negotiations were moving “too slowly.”

After Trump stated that a 10% tariff on $200 billion of Chinese goods would jump to 25% on May 10 while also raising the possibility of slapping a 25% tariff on $325 billion of imports from China, investors panicked: The Dow fell by more than 450 points Monday morning, though it appeared to be on the rebound later in the afternoon. China’s Shanghai Composite Index had dropped by nearly 5.6% at the close of trading.