Days after the U.S. and China struck an apparent trade truce, President Donald Trump threatened the nation with new tariffs, sending the stock markets into a downturn. Trump and Chinese President Xi Jinping on Saturday had committed to no new tariffs for 90 days as they tried to craft a broader trade agreement. But Tuesday, Trump called himself “Tariff Man” in a string of tweets that threw the accord with Beijing into doubt. Wary investors responded with a sell-off in stocks, concerned that a standoff between the two economic powers will slow global growth. “They actually want to see a positive resolution where the problem is solved so they don’t have to worry about it,” one investment strategist said.