In an interview on CNBC, Cooperman also said the country needs a more moderate president.
"If he listens to his advisors, hopefully, enough sane people in Washington will tell him 'let's back off on this trade stuff,'" the chairman and CEO of Omega Advisors hedge fund said on "Squawk Box."
The Trump administration decided last week to impose tariffs of 25 percent on steel imports and 10 percent on aluminum imports from Canada, Mexico and the European Union. The three U.S. allies quickly announced retaliatory measures.
Commerce Secretary Wilbur Ross defended the tariffs on Thursday, telling CNBC the stock market will "adjust" to any changes in U.S. trade policies. He also said that ending the tariff relief on Canada and Mexico reflects the lack of progress in the NAFTA talks.
Cooperman, who said he did not vote for Hillary Clinton or Trump during the 2016 elections, also said the United States needs a more moderate president, but he would not tell Trump "how to conduct himself."
"I would like someone to be more unifying. He can accomplish what he wants to accomplish and do it in a different manner," Cooperman said. "We need a centrist, we need a moderate, we need someone who unifies people together."
Cooperman said he would prefer someone in office like billionaire businessman and philanthropist Ken Langone, saying the Republican co-founder of Home Depot is "one of the finest human beings I've ever met." He added that Langone, now 82, is probably too old to run in two years.
"In November, you're going to find out from the American people [if] they are squarely concerned about the economy or are they concerned about the image of the country, integrity and things like that," Cooperman said.
In the interview, Cooperman also said he would sell stocks on a rise because the market is fairly valued.