Members of the Trump administration on Sunday defended the president's vow to shut down the U.S.-Mexico border, referring to a "crisis" in the number of migrants attempting to cross over.

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 threatened earlier this week to shut down the border in response to growing warnings from the administration about a crisis there.

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Trump said multiple times that he could close parts of the border unless Mexico's government immediately stopped illegal crossings. He also blamed Democrats for "weak immigration laws."

On Friday, he said there is "a very good likelihood" he will shut down the border.

"Mexico is going to have to do something; otherwise, I’m closing the border. I’ll just close the border. And with a deficit like we have with Mexico and have had for many years, closing the border would be a profit-making operation. When you close the border also you will stop a lot of the drugs from coming in," Trump added to reporters in Florida.

"It certainly isn’t a bluff. You can take the president seriously," White House counselor Kellyanne Conway Kellyanne Elizabeth ConwaySpecial counsel investigating DeVos for potential Hatch Act violation: report George and Kellyanne Conway honor Ginsburg Trump carries on with rally, unaware of Ginsburg's death MORE later said on "Fox News Sunday."

"Congress can fix the problem of immigration that they’ve failed to fix. This president is looking at the metrics," she said, adding that the U.S. has "never seen a surge" in immigration "like this."

Her comments came after Customs and Border Protection Commissioner Kevin McAleenan said Wednesday that immigration enforcement has reached a "breaking point."

McAleenan cited the apprehension of more than 4,000 migrants a day at ports of entry recently to argue that the system is strained and cannot handle anyone else.

Issues with backlogs of court cases and a lack of proper facilities to hold those who seek asylum in the U.S. have been increasing. Roughly 100,000 people arrive at the southern border every month, according to Department of Homeland Security tracking.

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 also appeared on the Sunday talk show circuit, telling ABC's "This Week" that it would take "something dramatic" for Trump not to shut down the border.

"When Jeh Johnson said it’s a crisis, I hope people now believe us. ... 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.

The move to shut off the border would be a massive escalation for Trump, who has centered much of his presidency around creating a border wall and hard-line immigration policies.

Closing the border would have significant consequences both for those seeking asylum in the U.S. and for U.S.-Mexico trade.

His messaging about threats from immigrants — that they cause crime and bring in drugs — closely mirrors his argument in favor of shutting down the government for over a month in an attempt to secure funding for a border wall.

Trump declared a national emergency in February to allocate roughly $8 billion in federal funds to construct additional miles of barriers to prevent further crossings after Democrats refused to provide his full request in the budget.

This is not the first time Trump has proposed closing the border in response to spikes in immigration. He threatened in November and in December to do the same but never followed through.

His tendency to issue the threat has made some question his resolve.

Sen. Dick Durbin Richard (Dick) Joseph DurbinTumultuous court battle upends fight for Senate McConnell focuses on confirming judicial nominees with COVID-19 talks stalled Senate Republicans signal openness to working with Biden MORE (D-Ill.) called the threat a "totally unrealistic boast" while on NBC's "Meet the Press."

"What we need to do is focus on what’s happening in Central America, where three countries are dissembling before our eyes and people are desperately coming to the United States," the Senate minority whip added. "The president cutting off aid to those countries will not solve the problem.”

The U.S. halted aid to El Salvador, Guatemala and Honduras on Saturday because of the number of migrants coming from those countries to the U.S. through Mexico.

Trump said on Friday that the countries "set up" migrant caravans to travel to the U.S. border.