“And it’s going to do nothing ― absolutely nothing ― to stop the flow of Central Americans into this country,” he added.

“The miles and miles of trucks waiting to come into the United States ― importing produce, manufactured goods, the hundreds of thousands of workers who work for U.S. businesses legally but live in Mexico ― all that’s going to be shut down,” Sandweg said.

Sandweg, who temporarily headed the federal immigration agency under the Obama administration, told CNN on Monday that the president has the authority to close down ports of entry but warned it would hurt Americans if he did.

John Sandweg, a former acting director of U.S. Immigration and Customs Enforcement , said that President Donald Trump ’s apparent plan to close the southern border would do “absolutely nothing” to curb the number of people illegally crossing to the U.S. from Mexico.

John Sandweg, former acting director of US Immigrations and Customs Enforcement, says President Trump potentially shutting down the US-Mexico border will do "nothing, absolutely nothing to stop the flow of Central Americans into this country." https://t.co/rSwIg19h8L pic.twitter.com/mq8Mwl3xBd

Trump on Friday repeatedly threatened to close the border if Mexico doesn’t do more to stop the flow of migrants heading toward the U.S. His administration has already reduced the number of asylum seekers admitted at ports of entry, which experts say causes more people to cross into the U.S. illegally.

“There is a very good likelihood that I will be closing the border next week,” he said Friday at a news conference at his Mar-a-Lago resort in Florida.

Acting White House Chief of Staff Mick Mulvaney said Sunday that it would take “something dramatic” for Trump to not shut down the U.S.-Mexico border this week.

A day earlier, the U.S. cut aid to El Salvador, Guatemala and Honduras ― three Central American countries that are home to many of the asylum seekers coming to the U.S. border.

Trump accused the Central American nations on Friday of having “set up” caravans of migrants and sending them toward the U.S. But experts say cutting aide to these three countries is counterproductive and will likely drive more migrants to the U.S.

What’s more, only a fraction of undocumented immigrants enter the U.S. through legal ports of entry, making Trump’s threat to close the southern border all the more baffling, Sandweg said Monday.

“What’s going on at the ports of entry is just lawful trade and travel,” he told CNN. He said the U.S. has “a process that has worked for decades” for handling people who illegally cross into the U.S. from Mexico but that the Trump administration isn’t dedicating enough resources to it.

“So it’s taking years” for asylum claims to be processed, Sandweg said. “Thus further incentivizing more to come.”

The southern border has seen a surge of undocumented immigrants crossing into the U.S. In February, over 76,000 people were apprehended at the border by U.S. Customs and Border Protection ― more than double the number in February 2018.

“The administration sees an opportunity in this crisis,” Sandweg said. “The immigration folks in the administration have never liked the asylum laws. They don’t like the idea that the United States provides a safe haven for people fleeing political persecution.”

He added that Trump’s long-promised border wall “makes no sense” and won’t be “terribly effective” at reducing the number of undocumented immigrants coming into the U.S.

“The majority of the people coming across are in the Rio Grande Valley ― and CBP will tell you this ― because of flood zones and other things in that particular part of the country, the wall is going to be in many places up to a mile inland, or half a mile. All these Central Americans need is just 2 feet of American soil to get their feet on.”

Sandweg added: “This is a different type of situation than we’ve ever dealt with at the border before. These people are not trying to sneak into the United States and evade capture. They want to surrender right away because they know that [the Department of Homeland Security] is currently overwhelmed. So, no, the wall is not going to do anything about it.”