A federal judge may rule Monday on a Trump administration request for more time to reunite immigrant families separated at the border.
More than 100 children under 5-years-old remain separated from their families.
Government lawyers said the Department of Health and Human Services would only be able to reunite half of the children by the Tuesday deadline.
DNA swabbing is used to match parents with their children.
The effort is complicated by the fact that two federal agencies involved did not initially share records with each other. The Trump administration has until July 26 to reunite all 2,000 children who were taken from their parents after they crossed the southern border.
The deadline comes as lawmakers ask for a list of all children separated from parents under the Trump administration’s zero tolerance policy.
They ask for the number of days of separation. They also ask whether officials have successfully contacted parents to notify them of their child’s location and whether the parent has been detained, deported or released. They say the names can be left off.
The senators also seek a detailed briefing.