United States immigration authorities have detained almost 2,000 children in the past six weeks, which may cause them irreparable harm with lifelong consequences, said Zeid Ra’ad al-Hussein, the United Nations high commissioner for human rights.

He cited an observation by the president of the American Association of Pediatrics that locking the children up separately from their parents constituted “government-sanctioned child abuse.”

“The thought that any state would seek to deter parents by inflicting such abuse on children is unconscionable,” Mr. al-Hussein said.