Beto O'Rourke (D-Texas) will stage a counter-rally across the street, defying the president's fear-mongering on immigration at the southern border.
Mulling their next move from the dusty Mexican town of Piedras Negras, just south of the Eagle Pass crossing on the USA side, the latest group of around 1,700 caravan migrants want to avoid a potentially months-long wait for a chance to plead their case for asylum.
Numerous migrants who may seek passage with smugglers in their journey through Mexico cross the border and turn themselves into USA authorities to seek asylum in the United States, a drawn-out court process that can take months or years to resolve.
Members of the caravan may have to wait weeks or months to request asylum.
But Mexican police and soldiers are holding the caravan in the factory and not letting them stay anywhere else, in part to prevent a mass attempt by migrants to cross the Rio Grande. Out of almost 2,000 migrants, only 139 have so far obtained their official cards allowing them to leave the shelter and travel freely throughout Mexico.
The area from Piedras Negras east to Nuevo Laredo has always been dominated by the now-fragmented Zetas cartel.
Almost 2,000 people want to seek asylum and enter the United States through Eagle Pass, but U.S. Customs and Border Patrol says it can only process 16 to 20 people per day.
Ten dead after fire breaks out in dorm for young football players
The cause is under investigation, but a player with the under-17 side attributed the fire to an air conditioner. Two of the injured youths were hospitalised in stable condition and one was in critical condition, she added.
In his lengthy Medium post, O'Rourke slammed Trump's "racist, inflammatory rhetoric" about the border and laid out reasons he thought USA policy had exacerbated immigration-related challenges.
The 250 troops moving to Eagle Pass come from stations in Arizona, Pentagon spokesman Capt. Bill Speaks said Wednesday.
U.S. Border Patrol agents rescued five Honduran migrants in Eagle Pass who were almost swept away while trying to cross the Rio Grande River illegally. In Eagle Pass, customs officials are processing roughly 12 to 15 applications a day, according to Piedras Negras officials.
"You never know what's coming in", Maverick County Sheriff Tom Schmerber said Tuesday. A 14-ft-high border fence does exist in Eagle Pass, but it is poorly maintained, with several gaps and even open gates along its two-mile span.
There was also no mention of declaring a national emergency declaration, as he hinted last week, to get the funds to build his border wall.
Images from local media showed US agents with riot gear and shields standing on a bridge separating Eagle Pass and Piedras Negras.