The precise structure of these bilateral and trilateral deals remains largely opaque. But it is highly likely that many are being settled outside the traditional oil trading system, either through currencies other than the US dollar or through informal barter arrangements. The United States dollar-dominated global oil trading system is being tested by the US-Israeli war on Iran and the closure of the Strait of Hormuz, as governments in major consuming nations turn to increasingly opaque deals with Tehran and Gulf producers to secure supplies.