At least 330,000 children are held in detention because of migration issues worldwide, and the United States alone is responsible for nearly one-third of the number, UN-linked human rights lawyer Manfred Nowak said on Monday.
Nowak is the lead author of a new UN Global Study on Children Deprived of Liberty. According to his team's findings, the US currently has some 103,000 children in detention, which includes unaccompanied minors, those detained together with their families, and those who have been separated from their relatives.
The US government did not respond to the questionnaire sent out by Nowak's team. However, he said that the number was based on latest available official data and "very reliable" additional sources. Talking to the AFP news agency, he also said the figure of 103,000 was a "conservative" assessment.
"Migration-related detention for children can never be considered ... in the best interest of the child," Nowak told reporters in Geneva. "There are always alternatives available."
UN expert slams Trump administration
According to the findings, the US authorities hold "far more" children than any other country where reliable numbers are available, Nowak said. The US detains about 60 out of every 100,000 children both over migration and other issues, such as pre-trial detention, compared to between 14 and 15 in Canada and five in Western Europe.
The US also remains the only nation in the world not to ratify the Convention on the Rights of the Child, a UN treaty adopted in 1989.
"Of course separating children, as was done by the Trump administration, from their parents and even small children at the Mexican-US border is absolutely prohibited by the Convention on the Rights of the Child," Nowak said. "I would call it inhuman treatment for both the parents and the children."
French minors still detained in Iraq and Syria
Washington did not immediately comment on the study's findings.
The UN researchers also found that at least 29,000 children, mainly linked with the "Islamic State" group, are currently detained in Syria and Iraq, including a particularly large number of French citizens.
The UN is set to release country-specific numbers on Tuesday.