President Trump is threatening to shut down the U.S. Mexico border, or at the very least, "large portions" of it, next week if Mexico doesn't halt all undocumented immigrants from entering the country.

Mr. Trump — who has threatened to shut down the border before and has yet to do so — expressed his frustrations via Twitter on Friday.

"If Mexico doesn't immediately stop ALL illegal immigration coming into the United States through our Southern Border, I will be CLOSING.....the Border, or large sections of the Border, next week," the president tweeted from Florida. "This would be so easy for Mexico to do, but they just take our money and "talk." Besides, we lose so much money with them, especially when you add in drug trafficking etc.), that the Border closing would be a good thing!"

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Mr. Trump reiterated that intention in a conversation with reporters at Mar-a-Lago Friday afternoon, saying "theres a very good likelihood" he does so.

"I will close the border if Mexico doesn't get with it," Mr. Trump said, adding he will have a news conference at the border in the next couple weeks.

It's unclear how Mr. Trump wants Mexico to stop the flow of migrants, and Mr. Trump has repeatedly threatened to shut down the border, as recently as Thursday, but he has yet to close ports of entry.

Meanwhile, CBS News Pentagon correspondent David Martin reports the Army Corps of Engineers says it is surveying 54 miles of border wall in Yuma, Arizona, and El Paso, Texas, to replace barrier there. These would be the first construction projects funded by the $1 billion in reprogrammed counter-narcotics funding after Mr. Trump's executive actions in February. The U.S. Army Corps of Engineers' engineer reconnaissance teams are working with U.S. Customs and Border Protection leaders.

The president's tweets come after Homeland Security Secretary Kirstjen Nielsen is concerned about a "system-wide meltdown" over immigration at the border, with historically high levels of migrants passing through putting a strain on the system. In a letter to members of the House and Senate, Nielsen wrote, "DHS facilities are overflowing, agents and officers are stretched too thin, and the magnitude of arriving and detained aliens has increased the risk of life-threatening incidents."

Mr. Trump is in Florida this weekend, where he's touring a dike and the state's water infrastructure before relaxing at his Mar-a-Lago club.