Larry Fink, the chief executive at BlackRock, which with $5.1 trillion is the world's largest investor, is sounding the alarm over the US stock market.
Since President Donald Trump's victory in November, US equities have reached new heights thanks in part to the optimism that has swept much of Wall Street.
The S&P 500 is up 10.9% since November 8, Election Day.
The S&P 500 financial sector index has gained 18.9%, buoyed by the president's proposals for tax reform, deregulation, and fiscal stimulus.
In an interview with CNBC Thursday morning, Fink said the high price of US equities does not match up with current economic and market conditions.
"We don't have the tax reform that we're expecting. If we don't see a true deregulation, I think the markets would have some setbacks there."
He added that the US economy is slowing down, and would probably grow less than 1.5%. "In fact, I think the first quarter, the US may be the slowest economy in the G7," he said.
"If you believe that it would be longer for these to transpire and we have an economy that is slower because of uncertainty, then I would say the market is, the US equity markets are probably higher than they should be," Fink said.
He's not the only one who thinks the stock market is too expensive. The minutes from the March meeting of the Federal Open Market Committee released Wednesday showed that many Fed leaders are concerned that the US equities are overpriced.
From the minutes:
"Broad US equity price indexes increased over the intermeeting period, and some measures of valuations, such as price-to-earnings ratios, rose further above historical norms. A standard measure of the equity risk premium edged lower, declining into the lower quartile of its historical distribution of the previous three decades. Stock prices rose across most industries, and equity prices for financial firms outperformed broader indexes."