"We just want to a way to get to our final goal, which is the border", he said.
Should the caravan make it to the border, it will face a sizeable US military presence - more than double the 2,000 who are in Syria fighting ISIS - whose mission will be largely a support role.
The president's warning comes after it was revealed his administration was reportedly told that "only a small percentage" of migrants would end up making it to the US border as part of the ongoing caravan making its way through Mexico.
The group started with about 120 people and has grown along the way. There are already 2,100 U.S. National Guard forces at the border, sent after a previous Trump request in April, and they are authorized to go up to 4,000. A caravan in the spring ultimately fizzled to just about 200 people who reached the US border at San Diego.
The legal implications are chilling as United States troops will be used in a domestic operation explicitly forbidden by the Posse Comitatus Act.
Mexican government officials recently released photographs of two Hondurans from the second caravan who they arrested and deported for crimes they said were committed in Honduras.
A migrant caravan walks into the interior of Mexico after crossing the Guatemalan border near Ciudad Hidalgo, Mexico on October 21, 2018.
"Get off! Get off!" police officer Benjamin Grajeda shouted to a group of migrants clinging to the side of a truck outside Juchitan.
Yesterday he repeated a threat to strip Central American nations of United States foreign aid if they fail to help him stop the caravans.
Terrence O'Shaughnessy, head of U.S. Northern Command, said Tuesday that the number of troops participating in Operation Faithful Patriot could rise above the 5,239 who have deployed or are preparing to deploy to the border.
Defence Secretary Jim Mattis, speaking to reporters during a visit by the South Korean defence minister to the Pentagon, rejected the criticism, saying that the military was deploying to support the Department of Homeland Security and Customs and Border Protection.
Trump ordered the latest troop deployment to the Southwest border earlier this week. "Many more troops coming". His claims of the makeup of migrants within the caravan are unsubstantiated. The French news agency reports the group was in the Mexican town of Tapachula, about 1,850 kilometers from McAllen, on Tuesday.
As of press time Trump's proposal received muted media coverage and was not referenced on the online front page of the New York Times.
Even so, many in the caravan remain hopeful they will make it and have been monitoring their actions to dispel any false rumours they are violent or threatening.
The president issued similar warnings Monday.