White House press secretary Jen Psaki responded to questions as to why migrants are not required to be vaccinated against COVID-19 before entry to the United States, but foreign nationals who arrive by airplane are, saying that the situations are not comparable. 

During the White House press briefing, Psaki was asked why those migrants crossing the U.S. southern border are not asked for proof of vaccination. 

US TO REQUIRE FOREIGN TRAVELERS TO BE VACCINATED, LIFTING 14-DAY QUARANTINE

The question came after the White House on Monday announced that the United States will now require all foreign nationals to be vaccinated, and show proof of their vaccination status, in order to enter the country.

"As individuals come across the border, they are both assessed for whether they have any symptoms, if they have symptoms, the intention is for them to have to be quarantined," Psaki said, referring to migrants crossing into the U.S. "That is our process." 

When pressed further, Psaki said the situations could not be compared. 

"They are not intending to stay here for a lengthy period of time," she said. "I don’t think it’s the same thing. It is not the same thing." 

Psaki’s comments come after U.S. Customs and Border Protection (CBP) shut down the port of entry in Del Rio, Texas, diverting legal trade and travel 57 miles to Eagle Pass, while also shutting down border checkpoints to screen for illegal immigrants and illicit cargo, following a surge in predominantly Haitian migrants camping there in squalid conditions. 

In Del Rio, officials have described an "out of control" situation as they scramble to cope with a flood of migrants that has spiked from 4,000 on Wednesday to now what lawmakers said was 14,878 as of Saturday afternoon. Fox News images have shown migrants streaming across the border by the hundreds for days.

DHS TO RAMP UP DEPORTATION FLIGHTS TO HAITI AS OFFICIALS SCRAMBLE TO CONTAIN DEL RIO MIGRANT SURGE 

On Saturday, DHS announced more agents and staff were on the way and that deportation flights are set to be increased in the coming days, while stressing that "our borders are not open" and that most migrants will be expelled via Title 42 public health protections.

"We are expelling individuals based on Title 42, specifically because of COVID," Psaki said Monday. "Because we want to prevent a scenario where large numbers of people are gathering, posing a threat to the community, and also to the migrants themselves." 

"So those are the policies we put in place," Psaki added, noting that the Centers for Disease Control and Prevention have recommended that Title 42 "remain in place, given we're facing a global pandemic." 

The administration has been facing a surge in migration since taking office, which has hit a high of more than 200,000 encounters a month in both July and August. The administration has blamed the Trump administration’s ending of legal asylum pathways, as well as "root causes" like violence, poverty and corruption.

Meanwhile, as for the new international travel regulations, the mandate is set to go into effect in early November. The mandate also lifts the 14-day quarantine requirement for foreign vaccinated travelers, but will require those individuals to test negative within three days of departure.

The CDC is currently determining which vaccines meet the U.S. standard for foreign travelers. 

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Meanwhile, border restrictions on nonessential travel between the U.S., Canada and Mexico have been extended again – through Oct. 21. 

Fox News' Peter Doocy and Adam Shaw contributed to this report.