The single European currency is facing its biggest crisis since it was launched more than a decade ago. The severe debt problems facing one of its members, Greece, has intensified the debate about the future of the euro, which binds together 17 members with some very different economic policies. Will it survive, and if it does, what changes might have to be made to the currency pact? While interest rates are set at a European level, taxes and spending are decided nationally. Some have called for tough action by governments to make member economies more alike - so-called convergence. Others say that eventually the eurozone will need to resemble more closely the US, with richer countries sometimes paying the bills of poorer ones through fiscal transfers. BBC News - Greece crisis: What now for the euro project?