India abandons US dollar for Iranian oil
Most oil sales throughout the world are denominated in United States dollars (USD). According to proponents of the petrodollar warfare hypothesis, because most countries rely on oil imports, they are forced to maintain large stockpiles of dollars in order to continue imports. This creates a consistent demand for USDs and upwards pressure on the USD’s value, regardless of economic conditions in the United States. This in turn allegedly allows the US government to gain revenues through seignorage and by issuing bonds at lower interest rates than they otherwise would be able to. As a result the U.S. government can run higher budget deficits at a more sustainable level than can most other countries. A stronger USD also means that goods imported into the United States are relatively cheap.
Another component of the hypothesis is that the price of oil is more stable in the U.S. than anywhere else, since importers do not need to worry about exchange rate fluctuations. Since the U.S. imports a great deal of oil, its markets are heavily reliant on oil and its derivative products (jet fuel, diesel fuel, gasoline, etc.) for their energy needs. The price of oil can be an important political factor; U.S. administrations are quite sensitive to the price of oil.
Political enemies of the United States therefore have some interest in seeing oil prices denominated in pretty much anything but the US dollar.