A USA official told Fox News the hundreds of soldiers are being sent to the area to offer “logistical support”, including providing tends and vehicles, with Defence Secretary James Mattis possibly signing deployment orders today.
Another official told Reuters the military has received a request from the Department of Homeland Security to send troops to the US-Mexico border.
The official, speaking on condition of anonymity, said the military was examining the request that could see between 800 and 1,000 troops deployed.
Any troops deployed would not be involved in “law enforcement” activities, something that would be prohibited by federal law dating back to the 1870s.
This restricts the army and other branches of the military for civilian law enforcement on US soil, inless specifically authorised Congress.
But the military can still provide support services to law enforcement and has done occasionally since the 1980s.
Currently, there are 2,100 National Guard troops on the southern border assisting Homeland Security.
On Thursday, US President Donald Trump tweeted: “Brandon Judd of the National Border Patrol Council is right when he says on @foxandfriends that the Democrat inspired laws make it tough for us to stop people at the Border.
“MUST BE CHANGED, but I am bringing out the military for this National Emergency. They will be stopped!”
The migrant caravan is still in southern Mexico – more than 1,000 miles away from the nearest entry point into the US.
Fox News reported there are around 7,000 migrants here, but many of those currently walking are suffering from exhaustion, dehydration and heat stroke in soaring temperatures.
The majority of those walking claim they are looking for a better life in the US and are escaping poverty and violence in Honduras.
But many told the news broadcaster they fear being attacked if they jump on a cargo train, or getting deported if they take the bus.
Caravan member Brian Colanders said: “They are going to walk as long as they can, or as far as they can.”
On Monday, Mr Trump published a series of posts on Twitter, declaring the US is now facing a “national emergency”.
President Trump wrote: “Sadly, it looks like Mexico’s Police and Military are unable to stop the Caravan heading to the Southern Border of the United States.
“Criminals and unknown Middle Easterners are mixed in. I have alerted Border Patrol and Military that this is a National Emergency. Must change laws!”
In a second tweet, he added: “Every time you see a Caravan, or people illegally coming, or attempting to come, into our Country illegally, think of and blame the Democrats for not giving us the votes to change our pathetic Immigration Laws!
“Remember the Midterms! So unfair to those who come in legally.”
And in a third post, the US President wrote: “Guatemala, Honduras and El Salvador were not able to do the job of stopping people from leaving their country and coming illegally to the U.S.
“We will now begin cutting off, or substantially reducing, the massive foreign aid routinely given to them.”
This is a breaking story. More to follow.