Texas National Guard soldiers stand guard at the U.S.-Mexico border on Jan. 7, 2023, as viewed from Ciudad Juárez, Mexico. JOHN MOORE/GETTY IMAGES

The Biden administration is deploying 1,500 active-duty troops to the southern border to provide operational support to U.S. immigration authorities as they grapple with a sharp increase in migrant crossings ahead of the termination of pandemic-era migration restrictions, the Department of Defense announced Tuesday.

The service members will be deployed for 90 days, and will not be tasked with any law enforcement duties like detaining or processing migrants, said Brigadier General Pat Ryder, a Pentagon spokesperson. Instead, the military units will play a supporting role, assisting with transportation, administrative duties, narcotics detection, data entry and warehouse support.

The deployment approved by Defense Secretary Lloyd Austin was requested by the Department of Homeland Security (DHS), which said the move was warranted due to "an anticipated increase in migration." In a statement Tuesday, the department said the presence of additional military units would "free up" border officials to "perform their critical law enforcement missions."

Military personnel, DHS stressed, "have never, and will not, perform law enforcement activities or interact with migrants." A federal law dating back to 1878 generally prohibits the military from conducting civilian law enforcement.

The move to send military units to the southern border is designed to ease some of the pressure on Customs and Border Protection (CBP) officials, who are preparing for a sharp increase in crossings once they can no longer expel migrants under Title 42, the public health restriction first enacted in March 2020. The policy is set to end on May 11, once the national COVID-19 public health emergency expires.

Troy Miller, the top official at CBP, recently told Congress that his agency is preparing for as many as 10,000 migrants to cross the southern border every day after the end of Title 42, which would almost double the daily average in March. Daily migrant arrivals have already increased to more than 7,000 in recent days.

The military has been asked to support U.S. border officials multiple times since 2006, under both Republican and Democratic administrations. Former President Donald Trump's administration authorized dozens of high-profile and often controversial deployments as part of a broader crack down on illegal border crossings.

Late last month, President Biden gave the Pentagon emergency authorization to assist Homeland Security officials in efforts to combat international drug trafficking.

Roughly 2,500 National Guard troops are already at the southern border to support CBP. One U.S. official said their mission will be unchanged by the new deployment.