During the conference on Friday afternoon, a lawyer for the American Civil Liberties Union, which filed a lawsuit challenging the separation of families, said the process was proceeding more slowly than necessary because the government is insisting on using the same vetting procedures that it uses for so-called unaccompanied minors — children, typically adolescents, who enter the United States alone and are released to an adult who claims to be a parent. In those cases, protections are needed to make sure children are not handed over to adults seeking to exploit them.

But such exhaustive protections, including home visits and the fingerprinting of every member of a household where a child will be residing, are slowing down reunifications, said the lawyer, Lee Gelernt.

“It doesn’t make sense,” Mr. Gelernt said. “You have taken the child from the parent.”

Last week, Judge Sabraw gave the government until July 10 to reunite children younger than 5 with a parent. He set July 26 as the deadline for older children.

The Trump administration began separating families who crossed the border illegally in the spring as part of its stepped-up enforcement measures along the border. Last month, the president issued an executive order halting the practice after it drew outrage from elected officials from both sides of the aisle as well as from the general public.

“There really has been a massive effort to get the resources in place and on the ground to make reunification happen,” Sarah B. Fabian, a government lawyer, said on Friday.

However, she added, “There are some groups for which the reunification process is more difficult.” In those cases, she said, more time would be necessary to link parent and child.

“The government does not wish to unnecessarily delay reunifications or burden class members,” the Justice Department said in its motion. “At the same time, however, the government has a strong interest in ensuring that any release of a child from government custody occurs in a manner that ensures the safety of that child.”