Mexico deployed hundreds of riot police on Thursday to intercept a caravan of more than 4,000 Central American migrants, following demands by President Trump that Mexio, Honduras, Guatemala and El Salvador intervene before he has to deploy US troops. 

"I must, in the strongest of terms, ask Mexico to stop this onslaught - and if unable to do so I will call up the U.S. Military and CLOSE OUR SOUTHERN BORDER!” Trump Tweeted Thursday morning. 

On Tuesday, Trump threatened to cut off aid to Guatemala, Honduras and El Salvador if they "allow their citizens, or others, to journey through their borders and up to the United States."

Mexico said in a Thursday statement that it would also seek assistance from the United Nations refugee agency for help coordinating with Central American governments of countries from which the migrants originated. 

Hundreds of federal police in riot gear fanned out on the international bridge in Suchiate, on the Mexican-Guatemalan border, as the caravan of several thousand Honduran migrants trekked toward the crossing.

Guatemala also sent police reinforcements to its side of the border, after Trump threatened to cut aid to the region, deploy the military and close the US-Mexican border if the migrants were allowed to continue.

A first group of several hundred migrants arrived late Wednesday in the border town of Tecun Uman, Guatemala, where they overflowed a local shelter, leaving many to sleep in the town square or on the street, an AFP correspondent said. -AFP

The new caravan, which began in the Honduran city of San Pedro Sula with 150 migrants, is the second caravan from Honduras this year. The first caravan was largely disbanded, though a few asylum seekers successfully made it to US soil and were taken into custody.