The New Tariffs Against Mexico Signal the U.S. Isn’t a Reliable Negotiating Partner

The Trump administration has sent a message to the world with its new tariff threats against Mexico: No deal is ever a done deal.

That effect may be bigger than the immediate 5 percent tax on Mexican imports set to go into force June 10 and escalate to 25 percent over time.

Mexico had seemed to resolve its trade tension with the United States, in the form of a reworked Nafta now known as the United States-Mexico-Canada Agreement, or the U.S.M.C.A. The deal was moving toward fruition after the United States lifted steel and aluminum tariffs on its North American neighbors just days ago, and lawmakers in all three countries began considering it.

The new tariff threats, announced by President Trump in a tweet on Thursday, are aimed at pressuring the Mexican government to do more to combat migrants traveling from Central America to the U.S. border to seek asylum. It’s an issue not really related to trade policy at all. But the tariff threats amount to a vivid signal, especially to allies, that there is no permanent trade peace with the Trump administration, and could have significant consequences for future trade negotiations.

If you are working in a trade ministry in Brussels, Tokyo or Ottawa, how much confidence would you have that any deal you strike with American negotiators will have staying power?

I don’t see how our trading partners will continue to negotiate with us as if we have any credibility going forward,” said Emily Blanchard, a trade economist at Dartmouth’s Tuck School of Business. “They’re going to have a much harder time selling any costly domestic reform or sacrifice that is a concession to the U.S., because the U.S. is acting like an erratic bully.”

The escalating trade war between the United States and China had put Mexico in a promising position, as a destination for businesses making decisions about where to locate their supply chains and wary of tensions with China. Mexico has higher labor costs than China, perhaps, but it has an appealing geographical proximity to the United States and the favorable trade relations that seemed to be codified by the U.S.M.C.A. deal announced at the White House last fall.

Even if the new tariff is canceled before it is scheduled to begin, the action sends a signal that any cross-border supply chain — for decades a crucial strategy for large multinational firms and quite a few smaller ones — is inherently risky.

Mexico and Canada looked like a safe harbor because you just signed U.S.M.C.A.,” said Philip Levy, a senior fellow on the global economy at the Chicago Council on Global Affairs. “This action is saying, no, there really isn’t a safe harbor.