Donald Trump lashed out on immigration again after being spurred by images of a "caravan" of Central American migrants headed for the US border.
The US president took to Twitter to attack Mexico for allowing the 1,500-strong group to march toward the United States.
He then threatened to abrogate the North American Free Trade Agreement, which groups the United States, Mexico and Canada, while demanding Congress pass tougher immigration legislation and support his plan for a wall along the Mexican frontier.
He also declared he no longer supported a replacement for the program that offered protection against deportation for about 700,000 undocumented immigrants, most of them Mexicans, who went to the United States as children.
Trump has sought to crack down on all immigration since taking office early last year, but some of his proposals have become tied up in courts and in Congress.
"As ridiculous as it sounds, the laws of our country do not easily allow us to send those crossing our southern border back where they came from," he tweeted in demanding action.
In fact, statistics show arrests of undocumented migrants soared since Trump took office while illegal border crossings plummeted. But processes to deport arrested illegal immigrants are more backed up than before.
The president has repeatedly tried to link immigration with crime, but activists accuse authorities of grabbing longtime residents with families and jobs for minor infractions.
Mexico's President Enrique Pena Nieto has demanded the United States keep talking despite disagreements over immigration. "We have been conducting serious negotiations," he said.
The "caravan" that has enraged Trump is an annual event organized by People Without Borders activists. This time there are 1,500 marchers, who say they fled El Salvador, Guatemala, Honduras or Nicaragua because of poverty and widespread violence by criminal gangs.
They set off on March 25 from the Mexican state of Chiapas for the US border, where many hope to apply for asylum.
Mexico's government described the caravan as a "demonstration that seeks to draw attention to the migratory phenomenon and the importance of respecting the rights of Central American migrants."
Trump became aware of the march at the weekend from watching television.