"How do you negotiate hard with your banker?" Asked the then US Secretary of State, Hillary Clinton. This phrase, collected in a cable revealed by Wikileaks, summed up Washington's complicated relationship with China, which controlled public debt of the largest world power worth a billion dollars. A decade later, the Asian country has slightly increased its portfolio of US bonds. But that has not prevented today President Donald Trump from using all weapons against his great global competitor, who also remains his biggest banker.