French President Nicolas Sarkozy and German Chancellor Angela Merkel have demanded more economic supervision of the eurozone in the wake of the Greek debt crisis, dpa reported. "For Economic and Monetary Union to remain a success story, dealing with this crisis alone will not suffice," the leaders of the two largest eurozone economies said in a joint open letter made public Thursday. The letter was addressed to Herman Van Rompuy, president of the European Council, and the head of the European Commission, Jose Manuel Barroso, and published on the eve of a eurozone summit, which will open late Friday in Brussels. Sarkozy and Merkel urged the leaders meeting in Brussels to consider several proposals, such as "reinforcing fiscal surveillance within the euro area, including by providing for more effective sanctions" for members with excessive budget deficits. They also proposed "broadening the surveillance to structural and competitiveness issues and (economic) imbalances." Merkel and Sarkozy repeated their earlier demands that regulation of financial markets be increased. "Market reactions during the last few days have amplified the crisis and provoked very large swings in the yields of some Euro area member states' sovereign bonds not aligned with the development of fundamentals," they charged. The two leaders also took the opportunity to criticize the recent downgrade of Greek bonds to junk status by the rating agency Standard & Poors. -- SPA