WASHINGTON – President Donald Trump on Friday threatened to close the southern border as soon as next week if Mexico doesn't "immediately" step up its efforts to block immigrants attempting to enter the U.S. illegally.

"There’s a very good likelihood that I’ll be closing the border next week," Trump told reporters gathered at his Florida resort on Friday. "I will close the border if Mexico doesn’t get with it."

Similar threats in the past have raised questions over the authority of the president to seal the border, the logistics of such an endeavor, and the widespread consequences it would have on Americans’ ability to trade, travel and even eat.

Closing the border “is something that would be devastating economically,” said Peter Boogaard, a former Homeland Security official in the Obama administration now working for FWD.us, a group that advocates on immigration and criminal justice.

“We’re talking about more than a billion dollars a day, including a huge percentage of the food that is in grocery stores,” Boogaard said.

Trump administration officials have sought to characterize the situation at the border as a crisis, even though apprehensions along the southern border are at historic lows.

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Border Patrol routinely apprehended more than 1 million people a year – peaking at 1.6 million in 2000 – throughout the 1980s, 1990s and 2000s. In 2017, the agency apprehended just over 300,000. It 2018, it apprehended just under 400,000.

On the other hand, border officials have reported an increase in migrant families. The Trump administration this week began releasing families from custody because processing centers can't cope with the large increase.

In the first five months of the fiscal year, agents in Yuma, Arizona, have apprehended 17,578 migrants traveling as a family. By contrast, in that same time period last year, they encountered 5,319 migrants. That's a 330 percent increase.

Department of Homeland Security Secretary Kirstjen Nielsen hit that theme Friday.

"We face a cascading crisis at our southern border," Nielsen said in a statement. "The system is in freefall."

Trump has brought up his calls for tighter border security several times this week. Energized by a summary of special counsel Robert Mueller's investigation that found "no collusion" with Russia in the 2016 election, Trump has been relitigating longstanding fights this week over health care, immigration and even disaster aid to Puerto Rico.

Previous examples of closing the border are rare.

President George W. Bush partially closed the southern border following the 9-11 attacks, requiring full inspections of every incoming pedestrian and vehicle that led to days-long waits. President Ronald Reagan temporarily closed ports of entry along the southern border in 1985 following the kidnapping and murder of a DEA agent in Mexico.

Contributing: The Arizona Republic