Billionaire investor Warren Buffett says the U.S. must rally around President-elect Donald Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE before he enters the White House.

“I support any president of the United States,” he told CNN’s Poppy Harlow in an interview published Friday. "It’s very important the American people coalesce behind the president.

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“That doesn’t mean we can’t criticize him or they can’t disagree with what he’s doing maybe,” added Buffett, who backed Democratic presidential nominee Hillary Clinton. "But we need a country united. He deserves everybody’s respect.”

Buffett said he is already skeptical about the practicality of portions of Trump’s economic agenda, however.

“Nobody can grow the economy in 4 percent in real terms over time,” he said of his fellow billionaire’s campaign pledge. "The math is too extraordinary.

“It’s a bad idea, a very bad idea, but I’m not going to say it is going to cause a recession,” the Berkshire Hathaway CEO added of Trump’s call for a 35 percent tariff on goods imported to the U.S.

Buffett added he would offer Trump his economic counsel if the Republican sought it out after his inauguration.

“I would do that with any president. I’ve never called a president in my life. So I don’t initiate them. But if any president asks me for help in any way, I mean, that’s part of being a citizen.”