STERLING, Va. (AP) — President Donald Trump on Sunday dangled the prospect of renewing his tariff threat against Mexico if the U.S. ally doesn't cooperate on border issues, while some of his Democratic challengers for the White House said the last-minute deal to avert trade penalties was overblown.

In a series of tweets, Trump defended the agreement heading off the 5% tax on all Mexican goods that he had threatened to impose Monday, but he warned Mexico that, "if for some unknown reason" cooperation fails, "we can always go back to our previous, very profitable, position of Tariffs."

Still, he...