GENEVA — The UN human rights office called on the Trump administration Friday to “overhaul” its migration policies and find alternatives to detention, saying that children should never be held in custody, even with their parents.

“While we acknowledge the US decision not to continue separation, we understand that the practice now will be to detain a child with the parents,” UN human rights spokeswoman Ravina Shamdasani told a Geneva briefing. “We have said that a child should never be detained in relation to their parents’ migration status.”

The US military has been asked to get ready to house up to 20,000 immigrant children, officials said Thursday, as President Donald Trump’s efforts to roll back a widely condemned policy of separating children from their parents were beset by confusion.