US leaders are demanding the rest of the world recognize economic sanctions and stop buying Iranian oil. The U.K., Germany, France, Russia, China, and India are among the nations who don’t fully support the sanctions and would rather not pay higher prices for oil elsewhere.
American officials more and more often resort to delivering ultimatums, both to adversaries and allies alike. Nations that do not follow orders stand to lose access to the US financial system and could face trade sanctions of their own. That is a serious threat.
The huge majority of international trading is underpinned by US. banks and the dollar. Other currencies and banking systems cannot offer the same level of liquidity and convenience.