Hedge fund billionaire Leon Cooperman said he thinks the market is overvalued, and that it is overlooking "a number of things."

Chiefly, he said, the market "is not recognizing the risks that we face: the China relationship deteriorating, the tremendous increase in debt in the system, certainly from the election, the virus issues," Cooperman told CNN.

"I am focused on something the market is not focusing on at the present time and that is: Who pays for the party when the party is over?" Cooperman said.

The deficit is growing at a rate "well in excess of the growth rate of the economy," he said. "To me, that means more of our nation's income will have to be devoted to debt service, which will retard economic growth in the long term," he said.

"If Democrats control Congress and the White House, I think that there's going to be a big increase in taxation which will not be a positive for the market," he said.

Cooperman isn't alone in his warnings about the market.

Strategists from Morgan Stanley, RBC Capital Markets and Societe Generale SA. warn that investors may be too complacent about upcoming risks to markets over the next couple of months.

As a run of positive catalysts comes to an end -- including improved clarity from earnings season, a new European Union recovery fund and the possibility of further U.S. fiscal stimulus -- the favorable environment for risk assets is expected to change, Morgan Stanley strategists led by Andrew Sheets wrote in a note Friday, Bloomberg reported.

The team suggested investors reduce exposure for the August-September “danger zone” when seasonality worsens for equities and credit, the U.S. presidential election comes into focus and an “exceptional” period of positive economic surprises likely moderates.

“Over the next two months, positive catalysts fade, seasonality gets worse and near-term risks emerge,” they wrote. They recommended investors consider raising cash balances and buying credit-default-swap index protection in the bond market. They also suggested looking at European assets which are more likely to outperform.

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