The international financial system has come in for some criticism, with the International Monetary Fund saying it still has a long way to go to fix itself.
At the World Economic Forum in Davos, Switzerland, IMF deputy director general Min Zhu said financial products remain complex and shadow banking continues to be unregulated.
He urged bankers and regulators to co-operate more closely.
But JP Morgan chief executive Jamie Dimon defended banks, though he said it's hard to understand how they work because businesses can be opaque because they're complex.
Mr Dimon argued better, not more, regulation is needed.
Another participant, UBS Bank chairman Axel Weber, called for a global regulatory standard that will allow banks to avoid fine-tuning their risk operations in individual countries.