The decision by the Trump administration was explained as a national security measure, a move that summoned sharp rebukes from all nations affected, including Mexico.
The administration also said it was conducting a similar investigation into imported cars — a market where the Mexican economy is deeply intertwined with the United States.
For renegotiations on the North American Free Trade Agreement, some experts think that the move on Thursday could heighten tensions between the nations during already tense talks. Now that the United States has taken concrete action, the stakes are higher, potentially leading Mexico and Canada to dig in their heels more in the face of American demands.
“Trump had delayed the tariffs on Mexico and Canada pending results from the negotiations, and threatening to impose them to pressure more,” said Jeffrey A. Weldon, director of the political science program at the Mexico Autonomous Institute of Technology. “Trump may have seen the end of the line.”
The tariffs are also unlikely to force the Mexican government’s hand, especially given current electoral dynamics. The candidate of the governing party, José Antonio Meade, is a distant third in polls and is unlikely to win. That means there is little pressure to sign a deal quickly simply to help his campaign.
In the short term, analysts expected that the trade battle now underway would quickly result in price increases on certain products on supermarket shelves in Mexico as the retaliatory tariffs take effect.
A greater, enduring fear, according to Enrique Dussel Peters, an economist at the National Autonomous University of Mexico, is that Mr. Trump will suddenly pull the United States from Nafta, as he has threatened.