WASHINGTON — The Pentagon is sending nearly 3,000 additional active-duty troops to the U.S.-Mexico border as President Donald Trump seeks to clamp down on illegal immigration and fulfill a central promise of his campaign, U.S. officials said Saturday.

His defense secretary, Pete Hegseth, has ordered elements of a Stryker brigade combat team and a general support aviation battalion for the mission, the Pentagon announced. The forces will arrive along the nearly 2,000-mile border in the coming weeks.

Fort Carson is sending 2,400 soldiers from the 2nd Stryker Brigade Combat Team, 4th Infantry Division, while another 500 soldiers from Fort Stewart’s 3rd Combat Aviation Brigade will also be deployed, according to the U.S. Northern Command.

The Strykers are medium-armored wheeled personnel carriers. That team will provide transportation and engineering support along with detection and monitoring but will not be involved in interdiction or deportation operations, Northern Command said.

The aviation brigade will help with the movement of personnel, equipment and supplies, it said.

Already, about 9,200 U.S. troops in total are at the southern border, including 4,200 deployed under federal orders and about 5,000 National Guard troops under the control of governors.

The new troops will “reinforce and expand current border security operations to seal the border and protect the territorial integrity of the United States,” the Pentagon said.

Trump is determined to expand the military’s role in his effort to shut down the border and send detained migrants back to their home countries.

Military personnel have been sent to the border almost continuously since the 1990s to help address migration, drug trafficking and transnational crime.

The Washington Post first reported on the new deployment.