A man reacts as people line up to withdraw cash from an ATM outside a Eurobank branch in AthensATHENS/FRANKFURT (Reuters) – Greece said it may impose capital controls and keep its banks shut on Monday after creditors refused to extend the country’s bailout and savers queued to withdraw cash, taking Athens’ standoff with the European Union and the International Monetary Fund to a dangerous new level. Greece’s banks, kept afloat by emergency funding from the European Central Bank, are on the front line as Athens moves towards defaulting on a 1.6 billion euros payment due to the International Monetary Fund on Tuesday. The European Central Bank added to the pressure by saying there would be no increase in its support of Greece’s crippled banking system.