Washington (CNN) There was a scramble inside the White House on Monday over President Donald Trump's threat to shut down the southern border, three people familiar with what happened tell CNN.

After acting chief of staff Mick Mulvaney said the President would follow through on his threat "unless something dramatic" happened, aides huddled in the West Wing with two goals: find a way to keep Trump from closing the border, and if that wasn't doable, figure out the logistics in case he does.

Administration officials have been unable to articulate when or for how long the President would close the border, whether that closure would apply to air travel and what it would mean for the US economy.

"It's something that I'm sure we'll be looking into and studying," Kevin Hassett, the chairman of the Council of Economic Advisers, told reporters Monday when asked about the potential impact of a closed border.

Trump is being privately advised by multiple people inside and outside the White House that closing the border is a bad idea. Advisers told him it's not a sustainable option, underscored how it would disrupt the economy and noted it would anger local border officials throughout the country. Trump sees it a different way -- and thinks the move could save the US money.

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