UAE's dollar swap threats show how brittle these US alliances can be

The most striking moment in recent talks between United Arab Emirates officials and U.S. Treasury officials in Washington wasn’t the Emiratis’ suggestion of a currency swap line, but the warning they attached to it. If the UAE runs out of dollars, Emirati officials reportedly told their American counterparts, it might be forced to use Chinese yuan instead of U.S. dollars for its oil sales and other transactions.The U.S. dollar’s dominance rests, in part, on its near monopoly over oil transaction...