Tehran has announced that purchase orders by merchants that are based on US currency would no longer be allowed to go through import procedures.
Source: Iran bans use of US dollar in trade — RT Business News
The deliberate shift away from the PetroDollar affects US’ role in the global economy. What the US can do in terms of imposing sanctions, and how other nations trade with each other in this fossil fuel (petrol) stands to change with such steps. Traditional enmities which have lasted on ideological grounds and managed through trade will spill over into other spheres. Those who anticipate war are not mistaken.