The United States is just one bad recession away from being right back at zero interest rates or even lower, Larry Summers warned on CNBC on Monday.

“It’s a very different world when everyone’s stuck at zero interest rates,” said Summers, a critic of President Donald Trump who served as former President Bill Clinton’s Treasury secretary and as an economic advisor for former President Barack Obama.

“We’ll have to think about stabilization policy. Institutions are going to have to think about their investment policy in a very different world when we have a black hole, zero interest rate world,” Summers said on “Squawk on the Street.”