President Trump on Saturday ordered 25 percent tariffs on all Mexican exports to the United States and a similar levy on all Canadian goods, except for a 10 percent tariff on Canadian energy. His move sent shock waves through both nations, whose leaders have warned that the tariffs will harm all three countries and disrupt their deeply interwoven economies.

On his first day in office, Mr. Trump had vowed to impose punitive tariffs on Mexican and Canadian exports on Feb. 1, to force the two countries to better secure their borders against the flow of undocumented migrants and drugs.

The tariffs target the United States’ closest neighbors and key trading partners. Mexico became the United States’ largest trading partner last year, exporting a variety of goods, including automobiles and avocados, while Canada is the largest foreign supplier of crude oil to the United States.

Mexican officials have criticized the tariffs, arguing that they will not only harm Mexico’s economy, but will also hurt U.S. companies that have production plants in Mexico, including General Motors and Ford. American consumers are also likely to see higher prices for fruits, vegetables and other products.

President Claudia Sheinbaum of Mexico said on Friday that the country was “prepared for any scenario.” She has suggested that Mexico could retaliate with tariffs of its own.

Here is what to know about the tariffs: