Constitutional crisis threatens to cause the collapse of the political system, the country's leaders have warned. The concerns have been triggered by Bosnian Serb leaders who have stepped up their demands for independence with a warning the country is no longer "sustainable". The growing ethnic divisions have raised fears of a return to the fighting which claimed the lives of up to 110,000 people between 1992 and 1995. Senior European and US officials have called an emergency meeting in Sarajevo on Tuesday to meet the country's leaders to find a solution. The crisis centres on attempts to overhaul the constitution...