Acting White House chief of staff Mick Mulvaney Mick MulvaneyMick Mulvaney to start hedge fund Fauci says positive White House task force reports don't always match what he hears on the ground Bottom line MORE said Sunday that it would take "something dramatic" for President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE to not shut down the U.S.-Mexico border.

“Something dramatic,” Mulvaney said on ABC's "This Week" when asked what it would take for Trump not to follow through on his threat of shutting down the southern border entirely.

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“When Jeh Johnson said it’s a crisis, I hope people now believe us. A lot of folks in the media… Democrats didn’t believe us a month ago, two months ago, when we said what was happening at the border was a crisis: a humanitarian crisis, a security crisis,” he said.

“One hundred thousand people coming across the border this month… that is a crisis,” he added.

NEW: Acting White House chief of staff Mick Mulvaney tells @jonkarl it would take "something dramatic" for President Trump not to close the U.S.-Mexico border https://t.co/GtOTcEQrgO #ThisWeek pic.twitter.com/VR9ICtDKci — This Week (@ThisWeekABC) March 31, 2019

Trump tweeted twice last week that he could close parts of the border unless Mexico's government immediately stopped illegal crossings.

He also continued blamed Democrats for "weak immigration laws."

The comments came after Customs and Border Protection (CBP) Commissioner Kevin McAleenan said last Wednesday that immigration enforcement has reached a "breaking point."

This is not the first time Trump has threatened to close the border. He threatened in November and in December of last year to do the same.