Members of the caravan, exhausted from the hours-long trek on foot from the Guatemalan border, mostly ignored police offers in Mexico to board buses heading to a migrant shelter because of suspicions they might be deported instead.
"Sadly, it looks like Mexico's Police and Military are unable to stop the Caravan heading to the Southern Border of the United States", Trump wrote in a post on Twitter, adding: "I have alerted Border Patrol and Military that this is a National Emergy (sic)".
US President Donald Trump on Monday (Tuesday NZ Time) vowed to cut off or "substantially" reduce aid to three Latin American nations, voicing fresh frustration as a growing caravan of migrants that originated in Honduras continued to make its way toward the US-Mexico border. At least 1,000 more remain at the border, waiting to enter the country, reported the EFE Agency.
Earlier this month, a caravan of 160 migrants set out from Honduras, telling media outlets that they were fleeing their homes due to widespread poverty and violence.
In another tweet, he blamed Guatemala, Honduras and El Salvador for not stopping people from leaving their countries.
According to the US Agency for International Development, US aid obligations this year are about US$53 million to Guatemala, US$20 million to El Salvador and US$15 million to Honduras.
Last week, Trump said he could mobilize the United States military and shut down the border if the migrant group didn't turn around.
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Last Friday, Saudi Arabia admitted that Mr Khashoggi did in fact die in the consulate, but claimed it had occurred during a brawl. They said: "Nothing can justify this killing and we condemn it in the strongest possible terms".
Stopping illegal immigration was one of the main promises Mr Trump made when was elected U.S. president.
The caravan formed in the Honduran city of San Pedro Sula.
The State Department says that they are concerned that these migrants may be victimized by human smugglers or others who would exploit them.
He said the migrants' rights must be protected as they break into Mexico and head north.
Donald Trump has ordered the military to be on alert over a US-bound migrant caravan as he declared a national emergency.
On Sunday, Homeland Security Secretary Kirstjen Nielsen said her department would be keeping an eye on any criminal elements that were infiltrating the group as it traveled to the US.
Trump had warned Mexico's government last week "in the strongest of terms", to halt the caravan's advance, and threatened to rip up a recently signed trade agreement with Mexico if Enrique Peña Nieto's government doesn't act to stop illegal immigration.