The EU's implicit guarantee that it will prevent debt-laden countries, such as Greece, from defaulting could hurt benchmark bonds as well as the euro. "[There is an] assumption no euro-zone country will be allowed to default. Because of that, they don't restructure and this is not sustainable," said Stephen Jen, head of currencies and macroeconomics at BlueGold. "There is a legacy cost of the problems which we are starting to discover now and the future cost of structural reform. This will affect the underlying performance of euro assets and euro itself."