Wilbur Ross, President Trump's commerce secretary, standing next to an American flag, read out a speech that was being transmitted to Berlin via video link. He demanded that Germany buy raw materials from the United States instead of from Russia, lower tariffs on automobile imports from the U.S. and ensure that America "obtain a larger share" of the European market. Otherwise, he added, the government in Washington, D.C., would have no alternative but to "engage in self-help." Less than a week before the G-20 summit is set to start in Hamburg, the risk is growing that the unpredictable U.S. president could turn the prestigious meeting of world leaders into a fiasco.