Political difficulties

In the present world, nations are not yet able to work together closely enough to be able to produce and support a common currency. There has to be a high level of trust between different countries before a true world currency could be created. A world currency might even undermine national sovereignty of smaller states.A currency needs an interest rate, while one of the largest religions in the world, Islam, is against the idea of interest rate. This might prove to be an unsolvable problem for a world currency, if religious views concerning interest do not moderate. This is not necessarily a fatal falw however, as a large number of religious adherents who oppose the paying of interest are able to take advantage of banking facilities in their countries which are able to cater to this. An example of this might be Islamic banking, which operates well enough in nations where the central bank sets interest rates for most other transactions.Having an interest rate is one of the fundamental laws of a market economy. Depositing of money is important because it lets the money be lent out where it is needed most, for instance when establishing a new company or buying a house for a family. In order to get strangers to lend each other money the creditors needs to get compensated for their risk taken and their good will. If not they would just spend the money, or keep it or invest it somewhere else. If you want to be without interest rate you need other ways to compensate depositors, and the compensation would have to be in the form of money, in other words an interest-look-alike