Sen. Ron Johnson (R-Wis.) said on Sunday said he’s questioning President Trump’s “endgame” in his approach to tariffs, saying the ongoing “volatility” isn’t good for businesses.

“One thing I learned in the private sector is unpredictability can work pretty well in the negotiation, but the private sector businesses want certainty. They want stability. They don’t like to see volatility,” Johnson said in an interview on ’s “The Hill Sunday.”

“And, so, I’ve just been questioning exactly what’s the endgame here? What’s the strategy?” he continued.

Johnson called himself an “unabashed free trader” and touted what he sees as the benefits of global trade.

“From my standpoint, I think trade is good. You obtain goods from people that have a comparative advantage of producing those particular goods, and you sell them things where we have the comparative advantage,” he said.

Johnson said there’s a place for targeted tariffs.

“I can understand that there could be some good uses for tariffs,” Johnson said. “President Trump has proven that, for example, when he threatened Mexico with tariffs if they wouldn’t cooperate with ‘Remain in Mexico.’ That helped secure the border.”

“So there’s certainly a use for it,” he continued, “but tariffs are a double-edged sword and a pretty blunt instrument.”

He also said he doesn’t like the idea of using tariffs as a source of revenue, which he said “just puts more revenue in the federal coffers,” when he thinks “we need to shrink the size of government” and reduce spending.

Commerce Secretary Howard Lutnick made news on the Sunday-show circuit this week when he said tariff exemptions for smartphones and other electronics will only be temporary.

“This is not like a permanent sort of exemption. [Trump’s] just clarifying that these are not available to be negotiated away by countries. These are things that are national security, that we need to be made in America,” Lutnick told ABC’s “This Week.”