WASHINGTON — For more than a year, Donald Trump rallied supporters by vowing to build a “big beautiful” wall along the nearly 2,000-mile-long border with Mexico, calling it crucial to stop migrants, drugs and criminals from entering the United States.

John Kelly, the president-elect’s choice to head the Department of Homeland Security, which is responsible for guarding the nation’s borders, said Tuesday that a wall won’t solve the problem.

Kelly, a retired four-star general, told his Senate confirmation hearing that cutting the flow of migrants and illegal drugs would require addressing rising violence and lack of opportunity in poverty-stricken countries in Central and South America, not just building a wall.

“A physical barrier in and of itself will not do the job,” Kelly told the Senate Homeland Security and Governmental Affairs Committee. “It has to be really a layered defense.