Europe is tense as President Obama arrives in Cannes for the G-20 economic summit. France and Germany have given Greece an ultimatum, demanding to know whether Greece plans to retain the euro currency before extending the debt-ridden nation any additional aid. "Does Greece want to remain part of the eurozone or not?" German Chancellor Angela Merkel said Wednesday. Greek Prime Minister George Papandreou agreed to push up a referendum on the EU bailout package from January to Dec. 4. The referendum may, however, fall apart before it takes place, as Papandreou faces a no-confidence vote in Parliament Friday.