The accord struck at an EU summit last week is the \"sole possible way to resolve Greece\'s debt problems,\" French President Nicolas Sarkozy said on Tuesday. \"Giving people a voice is always legitimate, but the solidarity of all the eurozone countries is not possible unless each one agrees to measures deemed necessary,\" he said. Sarkozy spoke a day after Greek Prime Minister George Papandreou\'s shock announcement that he would put the measures reached at the EU summit to a national referendum.