caravan of Central Americans that formed in southern Mexico in late March also drew the ire of Trump, who on Thursday threatened to use the military and close the southern border if Mexico did not halt the new march.

Such a move would cause chaos on the crossing, one of the world's busiest, and badly disrupt trade.

Speaking in Scottsdale, Arizona on Friday, Trump said he "appreciated very much" Mexico's efforts to stop the caravan.

"If that doesn't work out, we're calling up the military - not the (National) Guard - we're calling up the military," he told reporters. "They're not coming into this country."

Trump has also threatened to cut off aid to Honduras, Guatemala and El Salvador - some of the poorest and most violent countries in the Americas -if they fail to prevent undocumented immigrants from heading to the United States.

Their emigrants make up the bulk of people now caught trying to enter the United States illegally every year.

Several migrants at the Guatemala-Mexico border spoke of entire neighborhoods leaving their homes to join the trek after news circulated on social media of a call for a new "caravan" to Mexico six months after the previous one.

U.N. ASSISTANCE

Earlier, Mexican Foreign Minister Luis Videgaray and U.S. Secretary of State Mike Pompeo met in Mexico City and discussed the caravan, which set off from Honduras last weekend.

"It's a challenge that Mexico is facing, and that's how I expressed it to Secretary Pompeo," Videgaray told a joint news conference.

Pompeo said he and Videgaray spoke of the importance of stopping the