Defense Secretary James Mattis is expected to sign deployment orders as soon as Thursday that could send 800 or more troops to the border with Mexico to help border patrol authorities stop a caravan of migrants from Central America moving through Mexico to enter the US, according to three administration officials.
The officials said final details are being worked out including where the troops will come from and their specific tasks.
It is not yet clear if all or part of the new deployment will be federally activated National Guard forces or active duty troops.
The troops will not engage in lethal operations to stop the migrants. Instead they are expected to provide fencing, wall materials and other technical support at several key points along the border where it is believed the migrants may try to cross.
The troops will also provide tents and medical care for border authorities in those areas. The troops retain the right of self-defense, but border patrol officers will still be the ones physically stopping illegal migration, the officials said.
President Trump hinted at the upcoming effort with a Thursday morning tweet, saying "I am bringing out the military for this National Emergency."
The troops are expected to be in position next week.
This deployment is separate from an ongoing National Guard effort along the border to support border authorities with technical assistance. That mission has approximately 4,000 personnel authorized but only 2,100 are currently in place according to the Pentagon.
Organizers have said the migrants still don't know exactly which route they'll take. Much depends on the Mexican government and what routes the caravan is allowed to travel, whether its members are detained or held in certain areas and whether the group is provided with buses to speed their journey.
There's a possibility some members will split off and try to make their own way to the US-Mexico border. Others have decided to stay in Mexico -- or return to their home countries.
Mexican immigration authorities have already begun processing asylum requests for 2,727 Central Americans who arrived with the group, according to a joint statement released Tuesday by the Foreign Ministry and Interior Secretary Office.
Mexican immigration officials also provided assistance to 495 Honduran nationals, who voluntarily agreed to return to their home country, the statement said.
The safest route would take them to Tijuana, across the US border from San Diego. A large caravan that crossed Mexico in the spring -- and also drew ire from President Trump -- took more than 30 days to reach Tijuanafrom Tapachula, Mexico -- a city this caravan departed on Monday.
Right now the closest border crossing to this caravan would be between Matamoros, Mexico, and Brownsville, Texas, about 1,111 miles away from the group's current location. But heading that way is considered a more dangerous route.
Representatives from Amnesty International will travel to the southern Mexican state of Chiapas from October 23-26 to observe the migrant caravan's journey and the response of Mexican authorities, the watchdog said in a statement Tuesday.