SAN DIEGO — The Biden administration will seek to partially end the 27-year-old court supervision of how the federal government cares for child migrants traveling alone, shortly after producing its own list of safeguards against mistreatment, an attorney involved in the case says.

The Justice Department has told opposing attorneys it will ask a federal judge on Friday to terminate the so-called Flores agreement at the U.S. Health and Human Services Department, which takes custody of unaccompanied children within 72 hours of arrest by the Border Patrol, according to Leecia Welch, deputy litigation director at Children’s Rights, which represents children in the case.

The landmark settlement — named for a child immigrant from El Salvador, Jenny Flores — would remain in effect at the Border Patrol and its parent agency, the Department of Homeland Security, creating what Welch called a “piecemeal” dismantling. Attorneys for unaccompanied children will oppose the move, which would be subject to approval by U.S. District Judge Dolly Gee in Los Angeles.

The Justice Department declined to comment. Health and Human Services had no immediate comment.

Flores is a policy cornerstone, forcing children to be quickly released to family in the U.S. and setting standards at licensed shelters, including for food, drinking water, adult supervision, emergency medical services, toilets, sinks, temperature control and ventilation. It grew out of widespread allegations of mistreatment in the 1980s.

The move has the potential to strain President Joe Biden’s already rocky relationship with immigration advocates as the Democratic leader confronts an unprecedented surge in border crossings in an election year. Border arrests have topped 2 million in each of the last two budget years, including nearly 300,000 unaccompanied children.

Biden has tacked toward heavier enforcement as Republicans attack his handling of the border. His administration plans another rule aimed at denying more asylum claims during initial screenings, a potential prelude to actions for a broader border crackdown.

The bid to partially undo Flores would come less than three weeks after Health and Human Services published a rule establishing safeguards for child custody. Secretary Xavier Becerra said the rule, effective July 1, will set “clear standards for the care and treatment of unaccompanied (migrant) children.”

Welch said ending special oversight can prevent attorneys for children from inspecting Health and Human Services shelters and interviewing children in the department’s care.

“My only guess for why they would want to do this now is because Flores counsel is a thorn in their side,” Welch said. “We can go into (their) facilities whenever we want, we can talk to the young people there, and when they’re out of compliance we can file motions to enforce, and they don’t like that.”

Keeping court oversight for the Homeland Security Department would keep critical parts of Flores intact, including a 20-day limit on the Border Patrol holding unaccompanied children and parents traveling with a child. Border Patrol holding facilities have experienced extreme overcrowding as recently as 2021, and the Biden administration has steadfastly resisted calls to detain children and families beyond 72 hours.

When Flores took effect in 1997, caring for child migrants was within the full domain of the U.S. Immigration and Naturalization Service, which disbanded six years later with the creation of Homeland Security. Since 2003, Health and Human Services has taken custody of unaccompanied children within 72 hours of arrest. The split became a nightmare in 2018 when the Trump administration separated thousands of children from their parents at the border, and computers for the two departments weren’t properly linked to quickly reunite them.