Closely followed trader Art Cashin warned on Friday that Wall Street could witness a "major shudder" if President Donald Trump imposes a tariff on steel.
"I think people would worry about trade wars and where we are going from there," UBS' director of floor operations at the New York Stock Exchange said on CNBC's "Squawk on the Street."
Cashin spoke after Axios reported on Friday that the Trump administration is "hell-bent" on imposing tariffs on steel and other imports.
The White House did not immediately respond to CNBC's request for comment.
Cashin also said the market has given the White House some latitude on getting proposed policies passed, like a repeal and replacement of Obamacare and tax reform. But if Trump were suddenly to slap on tariffs, "you see a major shudder go through the market here," he said.
Regarding the Friday's trading session, Cashin said to watch out for an another possible surprise tech sell-off. U.S. stocks were higher on Friday but the stocks fell on Thursday after technology stocks rolled over.
"The Nasdaq looks far more neutral, which is where it was yesterday," he said. "So, you want to keep your eye on that and see how tech holds up."
—CNBC's Fred Imbert contributed to this report.