WASHINGTON (AP) — Defiant in the wake of a stinging budget defeat, President Donald Trump on Friday declared a national emergency at the U.S.-Mexico border, moving to secure more money for his long-promised wall by exercising a broad interpretation of his presidential powers that is certain to draw stiff legal challenges.

In his emergency proclamation, Trump painted a dark picture of the border as "a major entry point for criminals, gang members, and illicit narcotics" and one that threatens "core national security interests." Overall, though, illegal border crossings are down from a high of 1...