"I hope we pull back from the brink here because these tariffs will not be good for the economy, and I worry that it will slow, if not impeded significantly, the progress we were making economically for the country," he said.
McConnell added that he hopes it ends soon and that he is "not happy about the prospects of a trade war."
The comments came during an economic conference in his home state of Kentucky. McConnell pointed to the impacts that a trade war might have on local employer Toyota and on Kentucky farmers.
House Speaker Paul Ryan issued a strong statement on Thursday evening, writing, "I disagree with this decision."
Ryan added, "There are better ways to help American workers and consumers. I intend to keep working with the President on those better options."
One Republican senator, who asked not to be identified, complained Thursday about Trump's decision to impose the tariffs, 25% on steel imports and 10% on aluminum imports. "I don't like trade wars. There are no winners in trade wars. And this scares me," the senator said.
Sen. Bob Corker, the chairman of the Senate Foreign Relations Committee, as well as House Ways and Means Chairman Kevin Brady also spoke out against the President, creating a noticeable break between influential Republicans on the Hill from the White House.
On North Korea: 'You could get snookered'
McConnell also warned President Trump on the pitfalls of being "snookered" by North Korea. "My advice to the President is: if you're a great deal maker, be interested in the details. Because he has had inherited -- in my judgment -- a very bad deal with Iran, that he chose to walk away from." He also said that the United States should be wary of easing up on sanctions and without giving up anything.
McConnell said he remained "hopeful" that the talks will lead to denuclearization.
"And I think for these situations to work, you have to not want the deal too much," he said. "If you fall in love with the deal, and it's too important for you to get it, and the details become less