A controversial clampdown on immigration has caused nearly 2,000 children to be separated from their families at the US border over a six-week period.
Stories of weeping children torn from the arms of their frightened parents have emerged since a "zero tolerance" policy on illegal entries was enforced, with all cases now being referred for criminal prosecution.
Because the children are not charged with a crime, US rules state that they cannot be detained with their parents.
Politicians and religious groups have been among those criticising the policy, describing it as inhumane.
Some immigration campaigners have claimed women are being separated from infants, an allegation that US officials have denied.
The International Rescue Committee, a humanitarian aid group, said: "A policy of willing cruelty to those people, and using young sons and daughters as pawns, shatters America's strong foundation of humanitarian sensibility and family values."
The Department of Homeland Security have said children are well cared for after being separated from their parents, with officials disputing reports of disorder and mistreatment.
A battle in Congress is now brewing over the issue.
US attorney general Jeff Sessions has defended the policy by quoting from the Bible, and argued that the recent criticisms were not "fair or logical and some are contrary to law".
He said: "I would cite you to the Apostle Paul and his clear and wise command in Romans 13, to obey the laws of the government because God has ordained them for the purpose of order."
More from US
From 19 April to 31 May, a total of 1,995 minors were separated from 1,940 adults as they tried to enter the US between official border crossings.
Asylum seekers who go directly to official crossings are not separated from their families unless officials cannot confirm whether a child is related to the adult they are with, or if the safety of the child is in question.