MEXICO CITY: Dozens of migrant families are splitting up at Mexico's northern border as they struggle to secure U.S. asylum appointments on a government app beset by high demand and persistent glitches, migrants and advocates say.

The anxiety of separation is piling more pressure on families who have often taken perilous journeys through several countries to reach the U.S.-Mexico frontier, and now no longer know when they will reunite.

"It's horrible, I wouldn't wish this on any mother," said Venezuelan migrant Jennifer Santiago, who was admitted into Brownsville, Texas, 10 days ago separately from her son, Derwin.

The 15-year-old decided to turn himself in at the border after his pregnant mother could only secure a solo appointment, Santiago said. He remains alone in U.S. custody.

U.S. President Joe Biden's administration made the app, called CBP One, directly available to asylum seekers in mid-January, aiming to make asylum requests at the border safer and more orderly.

The challenges for families have struck a nerve for some migrant advocates who recall the separation of families under Republican former President Donald Trump, which the Democratic Biden administration heavily criticized.

The U.S. Department of Homeland Security said it is "committed to family unity" and that more than half the beneficiaries have been families. Recent app updates will simplify and speed up the process for families, a spokesperson added.

Appointments fill up in minutes every day.

The competition makes slots easier to find for individuals than for multiple people, encouraging parents to register for themselves, hoping their spouses and children can join later.

"It is extremely difficult, nearly impossible, for some of these families to get an appointment together," said Karla Marisol Vargas, a senior attorney with the Texas Civil Rights Project. "These are just very difficult choices."

The CBP One app, named after the acronym for Customs and Border Protection, offers the only way for migrants at the border to request exceptions to a COVID policy called Title 42 that since 2020 has restricted asylum access. Migrants previously needed advocacy organizations to apply on their behalf.

'A REALLY HARD MOMENT'

About 22,000 migrants were granted exceptions to Title 42 and allowed into the U.S. at land ports of entry in January, in line with recent months, including nearly half who used CBP One once the system went into place.

Title 42 is expected to be lifted in May, after which the Biden administration aims to admit at least 30,000 migrants per month, a Biden official told Reuters.

On a recent morning at a shelter in the Mexican border city of Ciudad Juarez, migrants awoke in the middle of the night to upload applications, including a selfie photo scan prone to slow processing.

As soon as appointments opened at 7 a.m., they tapped their smartphones anxiously, competing to sign up for slots quickly.

"It's so slow," one woman said in dismay.

Along the border, the daily frustration of error messages and frozen screens on top of spotty internet, outdated phones and confusion around the multi-step process is taking a toll.

For Venezuelan migrant Angeldry Galeno, six weeks of failed attempts to get an appointment with her husband and two-year-old daughter led to the painful choice to go separately.

Her husband traveled to the Mexican border city of Nogales alone last week for his appointment, scheduled for March 3.

"He said, 'let's take advantage of the opportunity ... at least one person will be on the other side,'" Galeno said in Ciudad Juarez, showing a selfie the three took on their last day together. "It was a really hard moment."