The Justice Department told a federal court in California Friday that the Trump administration may need more time in certain circumstances to reunite undocumented families separated at the southern border. On June 26, in response to a lawsuit filed to resolve the separation issue, that court gave the Trump administration 30 days to reunite children and parents. The court gave a July 10 reunification deadline for children under the age of five, and a deadline of July 26 for all other children. As of Thursday, Health and Human Services said "under 3,000" children were still separated from their families.

In Friday's court filing, the federal government asked the court if it will still be in compliance with the 30-day deadline if it struggles to meet it in cases in which it is difficult to confirm parentage. The federal government, the filing said, is now using DNA testing to make sure parents are reunited with children, and that can take time.

"HHS is working diligently to minimize the burdens of confirming parentage, and is expediting DNA verification," the DOJ said in the filing. "But given the possibility of false claims of parentage, confirming parentage is critical to ensure that children are returned to their parents, not to potential traffickers. Although HHS is moving expeditiously to undertake these DNA tests, that process takes meaningful time, even when it is expedited."

The DOJ also expressed concern about the reunification timeline as it determines whether a parent has a criminal history.

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"To confirm that an individual is neither 'unfit nor presents a danger to the child,' that the parent is 'available to provide care and physical custody,' and that the parent 'has not engaged in any activity that would indicate a potential risk to the child,' ICE and HHS must confirm whether an individual has any criminal history, including a history indicative of abuse," the federal government said in the court filing.

Last month, Mr. Trump, bowing to political pressure, signed an executive order halting the separation of families at the border. But that didn't resolve the logistical problems for families who had already been separated.