Mexico's president has insisted his government will not be provoked, after President Donald Trump announced escalating tariffs on all goods unless Mexico curbed illegal migration.
Andrés Manuel López Obrador described Mr Trump's slogan "America First" as a fallacy and said universal justice was more important than borders, reports BBC.
Stock markets saw sharp losses following Mr Trump's announcement.
Mr Trump declared a national emergency at the US-Mexico border in February.
He said it was necessary in order to tackle what he claimed was a crisis with thousands of undocumented migrants crossing the US southern frontier.
On Thursday, US border authorities in El Paso, Texas, said they had detained a group of more than 1,000 migrants - the largest single group agents had ever encountered.
Robert Perez, customs and border protection deputy commissioner, said their apprehension "demonstrates the severity of the border security and humanitarian crisis at our south-west border".
In tweets later on Friday, President Trump said the tariffs were also to encourage Mexico to "take back" the country from drugs cartels.