J.P. Morgan Chase CEO Jamie Dimon warns that the only financial market bubble he sees right now is in government red ink.

At the World Economic Forum in Davos, Switzerland, CNBC’s Andrew Ross Sorkin asked Dimon if he sees any frothy areas in the market. “Only in sovereign debt,” the bank chief responded.

 “Right now people think central banks around the world can do whatever they want. They can’t,” Dimon said. Inflation “would be a big negative surprise,” he said.

 “I think it’s very hard for central banks to forever make up for bad policy elsewhere. And that puts them in a trap,” Dimon said. “Do you know anyone who’s actually bought a negative interest rate bond?”

“I would never buy a negative rate bond. Not unless I was forced,” he added. “In history, whenever you see something like that, it doesn’t necessarily end well.”

For his part, Treasury Secretary Steven Mnuchin said on Thursday the U.S. government cannot sustain federal deficits growing at current levels and will have to slow the rate of spending.

As he acknowledged the administration of Republican President Donald Trump was considering additional tax cuts to stimulate the economy, Mnuchin blamed government spending - and Democrats in Congress - for the federal deficit.

In an interview with CNBC, Mnuchin said increased military and non-military spending was the cause of the deficits, not the tax cuts pushed through Congress by Trump in late 2017.