The Pentagon says an additional 2,100 troops will be sent to the U.S.-Mexican border to help with security.
Among them are 1,100 active-duty troops who will perform a variety of missions, including aerial surveillance and logistical and administrative support.
The Pentagon says the new acting defense secretary, Richard V. Spencer, approved the deployment.
Also deploying are 1,000 members of the Texas National Guard. They will be under state control. Most will assist Customs and Border Protection at the temporary adult migrant holding facilities at Donna and Tornillo in Texas.
The new deployments are in addition to the approximately 2,500 active-duty and 2,000 National Guard troops already deployed to the border.