Mexican President Claudia Sheinbaum said on Wednesday (Novemebr 27) Mexico would retaliate if U.S. President-elect Donald Trump followed through with his proposed 25% across-the-board tariff, a move her government warned could kill 400,000 U.S. jobs.

"If there are U.S. tariffs, Mexico would also raise tariffs," Sheinbaum said during her regular morning press conference, in her clearest statement yet that the country was preparing possible retaliatory trade measures against its top trade partner.

Mexican Economy Minister Marcelo Ebrard, speaking alongside Sheinbaum, called for more regional cooperation and integration instead of a war of retaliatory import taxes.

Trump's proposed tariffs could violate the USMCA trade deal between Mexico, Canada and the U.S., which the countries signed in 2020 when Trump was president.

Trump vows big tariffs on Mexico, Canada and China

Ebrard warned the tariffs would lead to massive U.S. job losses, lower growth and hit U.S. companies producing in Mexico by effectively doubling the taxes they paid. "The impact on companies is huge," he said.

The proposed tariffs would hit the automotive sector's top cross-border exporters especially hard, he added, namely Ford, General Motors and Stellantis, and push up vehicle prices for consumers by thousands of dollars.

Mexico is the United States' top trade partner and its automotive industry is the country's most important manufacturing sector, exporting predominantly to the United States. It represents nearly 25% of all North American vehicle production.