"Dealmaker" Trump to China: "Stop or we'll shoot ourselves!"

Donald Trump campaigned - in part - on his reputation as a deal-maker. While some have disputed his acumen for making business deals, and others have questioned the ethics of his tactics, he made a convincing case to some loyal supporters that he would make good trade deals. 

The key to it all has been trade with China. At first, it seemed Trump wanted a hard line and hoped to ensure that China would reciprocate our openness with more openness on their own part, and by stopping its alleged "currency manipulation" (an allegation with dubious support). Now, the goal is to coerce China into cooperating with sanctions against North Korea.
Tying US trade policy with China to China's own reciprocity, or to other factors ignores one important aspect of trade theory: When the US remains open to trade, it is US citizens who gain the most, and those gains are mostly independent of whether individual trade partners choose to reciprocate. This is the basic idea of the mutual gains from trade. Hence, threatening sanctions against China to try to get them to cooperate is a threat on a similar plane as telling the police, "Stop or I'll shoot myself!"