European Union leaders on Sunday agreed to change the bloc\'s treaty if necessary in the interests of economic convergence and discipline, EU president Herman Van Rompuy said. \"We decided to explore the possibility of limited treaty change,\" Van Rompuy said. \"The aim is deepening our economic convergence and strengthening economic discipline.\" Speaking after EU leaders held crunch talks to nail down a solution to the worst economic crisis in its history, Van Rompuy said there was general agreement to ramp up discipline to save the euro, even if difficult treaty change was needed. \"Limited means not a general overhaul of the institutional architecture,\" he said. \"We also said that we would need the agreement of all the 27 (member states) before we can decide on a treaty change. \"The most important thing is not to change the treaty, the most important thing is to strengthen economic convergence,\" he said. The previous day, German Foreign Minister Guido Westerwelle had called for an EU treaty change allowing nations that live beyond their means to be hauled before the European Court of Justice, an idea that failed to win wide support. \"We urgently need changes to the treaty so we can have a real stability union,\" Westerwelle said during talks in Brussels. Luxembourg Foreign Minister Jean Asselborn, though, said re-opening the EU\'s rule-book, the Lisbon treaty, which was a painful decade in the making, would lift the lid on a \"Pandora\'s Box,\" threatening the EU\'s very future.