The head of the Bank of Greece warned bankers last week to brace for a “difficult day” on Tuesday if the Athens government does not reach a deal with creditors at an emergency euro zone summit on Monday, two senior bankers told Reuters. Bank of Greece Governor Yannis Stournaras called a special meeting with top bankers on Friday to discuss the mounting crisis in the banking sector after a flood of withdrawals that passed a billion euros a day toward the end of the week.