Legendary hedge fund manager Leon Cooperman criticized President Donald Trump for attacking the Federal Reserve, adding that negative interest rates are destructive to the economy.

“I think the president is doing a lot of damage with all this assault on the Fed,” Cooperman said Thursday at the CNBC Delivering Alpha conference in New York. “I vote with the guys at the Fed that didn’t want to cut rates” this week.

Trump has repeatedly taken on Fed Chair Jerome Powell for not cutting rates more aggressively. On Wednesday, Fed policy makers lowered their main interest rate for a second time this year while splitting over the need for further easing, caught between uncertainty over trade and global growth and a domestic economy that’s holding up well.

The benchmark rate was lowered by a quarter percentage point to a range of 1.75% to 2%.

“Interest rates are already low. That’s not your problem. So I don’t understand investors’ fixation on the need for rates to come down,” Cooperman said on CNBC. “Negative interest rates are destructive to the system.”

Cooperman is also concerned about the leftward move by the Democratic candidates for president.

“I don’t like to shift to the left,” he said. “Looking out I’m concerned next year, particularly about the election.”

A victory by Democratic Senator Elizabeth Warren, who supports giving medicare to all Americans, would cause a bear market, he said on CNBC.