WASHINGTON (MarketWatch) - Despite the Dodd-Frank bank reform legislation and global efforts to strengthen banks under the Basel III capital accord, the global economy is still at risk from "too big to fail" banks, Boston Federal Reserve Bank President Eric Rosengren said Wednesday. "Some significant challenges remain to be addressed if we are to have a global banking system in which no institution is "too big to fail" given the collateral damage its disorderly demise would cause to economies and citizens," Rosengren said in a speech at a conference on the lessons of the recession hosted by his regional Fed bank. One issue is that foreign countries remain far apart on how to split up assets of a large international institution if it were to fail, he said. And governments must address the issue that some large banks, particularly in Europe, rely on short-term wholesale funding that can evaporate in times of stress, he said. Another issue is that some countries have decided to protect only the domestic operation of their banks, he said. And regulators must be more proactive in forcing banks to retain and raise capital in times of stress, Rosengren added.