“At the end of the day, the president is going to secure the border one way or another,” Mr. Mulvaney said on “Fox News Sunday.”

“We have been hoping for months to do it through legislation with Democrats because that’s the right way for the government to function, but at the end of the day the president’s commitment is to defend the nation, and he’ll do it either with or without Congress,” he said.

The president said that if Congress doesn’t come up with a “fair” deal on homeland security funding in the next three weeks, he could invoke emergency powers to get his desired U.S.-Mexico border wall built, or try to orchestrate another partial shutdown.