Jamie Dimon, chairman and chief executive officer of J.P. Morgan Chase, is bullish on the U.S. economy, which is in the latter stages of one of the longest expansions in history.



But when asked Monday on CNBC's "Closing Bell" what the single biggest risk to the economy is, Dimon had two answers. First, the U.S. trade dispute with China, if it escalates into a full-blown war, would erase much of the progress the Trump administration has made, he said.

And then there's the unwinding of unprecedented efforts by central banks around the world a decade after the 2008 financial crisis. Dubbed "quantitative easing," the Federal Reserve and other central banks purchased trillions of dollars of government bonds and other securities to help nurse the economy back to health. They are now starting to reverse course. Dimon told CNBC that he is concerned about what happens when that support is pulled back.

"I don't want to scare the public, but we've never had QE," Dimon said. "We've never had the reversal. Regulations are different. Monetary transmission is different. Governments have borrowed too much debt, and people can panic when things change."



Dimon, 62, has also previously warned of the possibility that the Fed will have to hike interest rates faster than expected, slamming the brakes on growth. The recurring theme: policymakers are in uncharted waters. Adding to the risk is the fact that the administration is looking at imposing another round of tariffs on $200 billion in Chinese goods. Dimon said Monday that he told the administration that he and other business leaders disagreed on the tactics, but that President Donald Trump "obviously doesn't agree with us."