President Donald Trump said Wednesday that the number of troops he is sending to the U.S.-Mexico border could grow to as many as 15,000 active duty and National Guard personnel, putting the deployment on par with the military’s wartime operations in Afghanistan.

The number of troops would include the initial wave of 5,239 active duty troops, 2,100 National Guard forces already there, and another 2,000 to 3,000 on prepare-to-deploy orders. It would eclipse any previous border deployment in recent memory by administrations that have also sought to quell either violence or immigration influxes at the border.

U.S. Northern Command chief Air Force Gen. Terrence O’Shaughnessy told reporters Tuesday that the number of forces at the border could grow, but he did not indicate that the number may double within days.

O’Shaughnessy did not have a cost estimate on Tuesday. However, a previous deployment of 6,000 troops from 2006 to 2008 cost $1.2 billion, the U.S. Government Accountability Office has reported.

The forces are being dispatched to the border to deter two migrant caravans, each with several thousand migrants, headed to the U.S. through Mexico.