U.S. President Donald Trump’s economic advisor Gary Cohn is concerned about possible steel and aluminum tariffs, because he knows how markets will react if they’re imposed, according to a former Wall Street investment banker.

“As a purely economic guy, as a former banker and president of Goldman Sachs, Gary is very highly attuned to what the markets’ reaction to these types of tariffs will be,” William Cohan, who is also the author of House of Cards, told BNN in an interview Tuesday.

Reports swirled earlier in the day that Cohn was threatening to quit his White House job if the Trump’s proposed duties of 25 per cent on steel and 10 per cent on aluminum become a reality.

Trump took to Twitter to say there may be upcoming changes to his staff, but denied any chaos in the White House, saying “people will always come & go and I want strong dialogue before making a final decision.”

Cohn has reportedly been calling on executives from U.S. companies that depend on the metals to meet this week with Trump to try to blunt or halt the tariffs.

“[Cohn] probably believes that he can persuade Donald Trump to move off of this unreasonable position,” Cohan said. “Whether this will be a final straw for Gary – who knows.”

Cohan said saying goodbye to Cohn would be “another negative thing for Trump” but that he will survive the loss.

“Donald sort of muddles through and survives everything,” he said. “He’s like sort of a cockroach after a nuclear bomb goes off. He’s an ultimate survivor.”  

With files from Bloomberg News