ABC News has learned that two 82nd Airborne units are expected to be deployed along the United States, Mexico border along with 5,200 troops over the next several days.
One of the air units is expected to head to Davis-Monthan Air Force Base in Tucson. The other is expected to head to Lackland Air Force Base in Texas.
Additionally, ABC News has learned an additional 2,000 troops have been placed on "prepare to deploy" orders in case they are needed, according to a U.S. official.
The 5,200 troops being sent reportedly includes 1,700 troops that will be headed to Arizona.
The additional troops will provide logistical and other support to the Border Patrol, and will bolster the efforts of the approximately 2,000 National Guard forces already there. The new forces are expected to provide logistical assistance such as air support and equipment, including vehicles and tents.
National Guard troops routinely perform those same functions, so it is not clear why active duty forces are being used.
President Donald Trump for the past week has been calling attention to the caravan heading by foot into southern Mexico, but it is still hundreds of miles from U.S. soil.
The National Guard is often used by states to help with border security. But active-duty troops are rarely deployed within the United States except for domestic emergencies like hurricanes or floods.