"Mexico braces for a trade war with Washington," read the headline in the Financial Times on Tuesday.

Let's hope not, because a trade war triggered by President Donald Trump would be an act of pure economic aggression, unjustified either by the United States' economic and political interests or by Mexico's behavior. It would be the economic equivalent of Russia's seizure of the Crimea, a raw exercise in bullying.

Our interests here are plain. The basic need is to foster a prosperous Mexico that will provide expanding markets for our exports and, at the same time, create jobs and higher incomes that keep Mexicans from migrating to the U.S. (Net illegal immigration from Mexico has already halted.) Although a border wall is a legitimate way of curbing illegal immigration, it would be ineffective against a collapsing Mexican economy.