Mr. Trump has shown no sign that he plans to retreat from the trade action. On Monday, he used the tariffs to threaten two of the United States’ closest trading partners, saying in a tweet that the tariffs would only “come off” of Canada and Mexico if a new and “fair” multilateral trade pact was signed.

The statement continued Mr. Trump’s running Twitter defense of the tariffs, which he has positioned as necessary to help the United States protect itself against foreign competitors. But his administration continues to sow confusion over the breadth, scope and legality of the tariffs on steel and aluminum that Mr. Trump announced last Thursday. The White House has said those tariffs would apply to imports from all countries with no exemptions.

Mr. Trump’s tweet came as the United States, Mexico and Canada are wrapping up the seventh round of talks over the North American Free Trade Agreement in Mexico City. Negotiators have continued to clash over provisions in the pact, including rules for auto manufacturing, and the United States has continued to insist on changes that its trading partners say are nonstarters.

“We have large trade deficits with Mexico and Canada,” the president tweeted Monday. “NAFTA, which is under renegotiation right now, has been a bad deal for U.S.A.”