About 1,400 children of some 2,500 separated from their parents at the US-Mexican border have been reunited with their families, the US government has said in a court filing.
Government lawyers said 711 other children were not eligible for reunification with their parents as a court-ordered deadline to return all children to their parents elapsed.
In 431 of these cases, the families could not be reunited because the parents were no longer in the United States.
The parents and children were separated as part of US President Donald Trump's "zero tolerance" policy towards illegal immigration.
Many of them had crossed the border illegally, while others had sought asylum at a border crossing.
The American Civil Liberties Union, which brought the case against the government, said in the court filing that data showed "dozens of separated children still have not been matched to a parent."
ACLU attorney Lee Gelernt accused the government in a statement of "picking and choosing who is eligible for reunification" and said it would "hold the government accountable and get these families back together."
In a call with journalists after the court filing, US Department of Health and Human Services official Chris Meekins said it was awaiting guidance from the court about how to proceed with the children of 431 parents no longer in the United States.
The Office of Refugee Resettlement is an agency of department.
The government did not say in the call or in its court filing how many of those parents were deported.
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One immigrant, Douglas Almendarez, said he believed that returning to Honduras was the only way to be reunited with his 11-year-old son.
"They told me: 'He's ahead of you'," said Mr Almendarez, 37, in the overgrown backyard of his modest soda shop several hours drive from the Honduran capital of Tegucigalpa. "It was a lie."
The ACLU said the government has not yet provided it with information about the reunifications of children aged five to 17 with their parents, including the location and timing of them.
"This information is critical both to ensure that these reunifications have in fact taken place, and to enable class counsel to arrange for legal and other services for the reunited families," it said.
