The United Nations on Tuesday urged Washington to immediately halt its controversial practice of separating asylum-seeking Central American immigrant children from their parents at the southern border.
The UN rights office said it was "deeply concerned" over the "zero tolerance" policy introduced by the administration of US President Donald Trump in a bid to deter illegal immigration.
Spokeswoman Ravina Shamdasani warned the US policy had "led to people caught entering the country irregularly being subjected to criminal prosecution and having their children -- including extremely young children -- taken away from them as a result."
She said information received from US civil society groups indicated that several hundred children had been separated from their parents at the border since October, including a one-year-old.
"The US should immediately halt this practice," she told reporters in Geneva.
"The practice of separating families amounts to arbitrary and unlawful interference in family life, and is a serious violation of the rights of the child," she said.
"The use of immigration detention and family separation as a deterrent runs counter to human rights standards and principles," she said.
Shamdasani stressed that children's rights were "generally held in high regard" in the United States, but she lamented that the country was the only one in the world that had not yet ratified the UN Convention on the Rights of the Child.
Despite this, she insisted that Washington was bound by international human rights laws that its current practices were flouting.
"The child's best interest should always come first, including over migration management objectives or other administrative concerns," she said.
"It is therefore of great concern that in the US, migration control appears to have been prioritised over the effective care and protection of migrant children."
"Detention is never in the best interests of the child and always constitutes a child rights violation," she said, calling on Washington to "adopt non-custodial alternatives that allow children to remain with their families."
The US says the policy aims to stem a surge of poor families mostly from Guatemala, El Salvador and Honduras pouring into the United States.
Citing the daily violence in their home countries, thousands each week cross the US-Mexico border and immediately turn themselves in to authorities asking for asylum.
William Spindler of the UN refugee agency stressed Tuesday that "the right to claim asylum is a fundamental human right... and it is also part of the law in the United States."