As Mexican authorities do little to stop the 'migrant caravan' from cross southern Mexico, Defense Secretary James Mattis is reportedly preparing to order an additional 800 troops to the southern border as soon as Thursday, CNN reported.

The order comes after President Trump threatened earlier this month to send troops to the border to stop the migrant caravan, which has swelled to more than 10,000, according to some reports.

Final details are reportedly being worked out, including where the troops will come from and where they will be stationed. For example, it's unclear how many - if any - of the troops will be National Guard. According to CNN, they will mostly provide support services like building tents and running supplies for border patrol agents, who are still tasked with subduing illegal immigrants.