Democrat proposals to hike taxes could derail the economic expansion in the U.S., Stephen Schwarzman, chief executive officer of private equity giant Blackstone Group, said Monday.

Schwarzman was asked to name “stupid mistakes” that could hurt the U.S. economy.

“If there’s dramatic change in the tax area, if the Democrats win, if a lot of the things that some of their candidates are talking about, that would be a disincentive,” Schwarzman said in an interview with Bloomberg Television from the Milken Institute Global Conference in Los Angeles. “That could have a certain psychological shock value and logic would say that would slow the economy.”

Schwarzman said that raising interest rates could also derail the economy but downplayed the risk.

“People worry so much about the Fed doing the wrong thing,” he said. “The Fed is the guardian of the system, they’re not the enemy of the system.”

Schwarzman said that the Fed had made a mistake by raising rates and sounding too hawkish last year but had quickly corrected course.

Schwarzman is one of President Donald Trump’s strongest supporters on Wall Street and reportedly talks to the president regularly.