President Trump on Friday threatened to close the Southern Border next week if Mexico does not “immediately stop” the record-breaking surge of illegal immigrants flooding into the United States.

Trump's warning comes as Customs and Border Protection officials say March is on pace to exceed 100,000 border apprehensions -- the highest monthly total in a decade. According to CBP, this week alone, agents have more than 12,000 migrants in custody.,

“The DEMOCRATS have given us the weakest immigration laws anywhere in the World. Mexico has the strongest, & they make more than $100 Billion a year on the U.S.,” Trump tweeted. “Therefore, CONGRESS MUST CHANGE OUR WEAK IMMIGRATION LAWS NOW, & Mexico must stop illegals from entering the U.S. through their country and our Southern Border.”

“Mexico for many years made a fortune off of the U.S., far greater than Border Costs. If Mexico doesn’t immediately stop ALL illegal immigration coming into the United States through[sic] our Southern Border, I will be CLOSING the Border, or large sections of the Border, next week.”

He continued: “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!”

The president’s tweet comes after similar threats earlier in the week to close the Southern Border, with Trump accusing Mexico and Central American nations of doing “nothing” as illegal immigration surges.

Trump’s initial warning came following comments made by U.S. Customs and Border Protection Commissioner Kevin McAlleenan, who said this week that the border was at its “breaking point,” noting that there are not enough agents to respond to the flow of illegal immigrants crossing the U.S.-Mexico border.

“That breaking point has arrived this week at our border,” McAleenan said during a visit to the border in El Paso, Texas. “CBP is facing an unprecedented humanitarian and border security crisis all along our Southwest border.”

His agency also tweeted that they saw the highest number of "apprehensions and encounters" in over a decade this week -- over 4,000 in one day: "#CBP saw the highest total of apprehensions and encounters in over a decade on Monday, with 4,000 migrants either apprehended or encountered at ports of entry in a single day. Yesterday, that record was broken again—4,117 in a single day."

Last month, more than 76,000 migrants were detained, marking the highest number of apprehensions in 12 years. That figure includes more than 7,000 unaccompanied children. More than 36,000 migrant families have arrived in the El Paso region in fiscal 2019 with about 2,000 at the same time last year, according to CBP data. The influx has prompted new challenges for Border Patrol agents.

And according to new data, the number of adults crossing the border illegally with children has surged. During the first four months of the year, CBP apprehended more than 136,000 migrants made up of adults and children who crossed illegally, marking a new record.

Meanwhile, the president, whose paramount 2016 campaign promise was to build a wall along the U.S.-Mexico border, declared a national emergency in a bid to free up funding for the barrier along the border. This month, the president issued his first veto on a Democrat-backed measure to cancel the emergency.

When asked about his comments, the president said he was serious.

"Mexcio can stop them, but chose not to," he told reporters Friday. "So they're going to stop them, and if they don't, we'll close the border, and we'll keep it closed for a long time."

He added: "I'm not playing games."

On Tuesday, House Democrats failed to override Trump’s veto, allowing Trump to move forward with the issue.

Trump had declared the border emergency under a law that lets him shift budget funds to address dire situations. His plan is to shift an additional $3.6 billion from military construction projects to work on border barriers. Congress voted this year to limit spending on such barriers to less than $1.4 billion, and Democrats accused Trump of ignoring lawmakers' constitutional control over spending.

Fox News' Kristin Brown, Louis Casiano, Andrew O'Reilly and The Associated Press contributed to this report.