Dimon: 'I'm a real long-term bull' on US economy

What worries JPM's Jamie Dimon

Cancer can't keep Jamie Dimon down, and he thinks there isn't a lot that will keep the U.S. economy down.

However, he sees one thing that could derail the recovery: The $3.2 trillion ($15 trillion globally) nonbank financial system, or "shadow banks."

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The JPMorgan Chase CEO spoke Friday at the Institute of International Finance membership meeting in Washington, D.C., and delivered a mostly upbeat message.

However, asked what keeps him up at night, he said nonbank lending poses a danger "because no one is paying attention to it." He said the system is "huge" and "growing."

Nonbank lending was a contributing factor in the financial crisis due to firms lending money to low-quality borrowers who then defaulted on mortgages in droves.

He said, though, that the long-range prospects are good for the U.S.

"I'm a real long-term bull on the U.S. economy," he said on a panel with other Wall Street banking heavyweights, including Morgan Stanley CEO James Gorman and Bank of America CEO Brian Moynihan, in a discussion about the future of finance.