A civil rights group asked a U.S. judge to order the Trump administration to reunify more than 2,000 undocumented children taken from their immigrant parents and halt all future separations of families crossing the border to seek asylum.

President Donald Trump's June 20 executive order purporting to reverse his child-separation policy has "explicit loopholes" that will prevent all families from being reunited and allow separations to continue, the American Civil Liberties Union said in a filing Monday in federal court in San Diego.

The New York-based group, which sued in March to block the policy, contends that some of the children are babies and toddlers whose parents haven't been able to locate or speak to them since they were apprehended. One separated child was only 4 months old and another baby was taken from her mother while breastfeeding, the ACLU says.