The Trump administration wants advocacy groups to take the lead in helping to reunify migrant parents separated from their children at the U.S.-Mexico border, shifting the burden away from the federal government.

In response to the American Civil Liberties Union, which is representing migrant families, the Justice Department argued in a federal court filing Thursday that the nonprofit group can use its "considerable resources" and its network of law firms, volunteers and nongovernmental organizations to help in the process.

That includes making sure every migrant parent gets access to an attorney and to determine the best way for reunification to occur, according to the filing in U.S. District Court in San Diego.

But while ACLU lawyers responded that the group wants to be involved, it disagreed with the premise of the Trump administration's request because it was "the government's unconstitutional separation practice that led to this crisis" and federal officials are the ones with "far more resources."

"The government appears to be taking the remarkable position that it is the job of private entities to find these parents, and it can largely sit back and wait for us to tell them when we find people," Lee Gelernt, deputy director of the ACLU's Immigrants' Rights Project, said in a statement Friday.

An administration official not authorized to speak about litigation strategy said, "The administration’s filing simply asks the court to require the ACLU to determine the wishes of and fulfill their obligations to their clients, as they have repeatedly represented in court that they would."

The filing also mentioned how many children remain separated from their parents, most of whom have been fleeing violence and crime in Guatemala, El Salvador and Honduras.

Of about 2,550 children ages 5 to 17 who were removed from their parents after crossing the U.S.'s southern border; as of Thursday more than 570 are still in the custody of the U.S. Department of Health and Human Services and in government shelters.

The filing also mentioned how many children remain separated from their parents, most of whom have been fleeing violence and crime in Guatemala, El Salvador and Honduras.

Of about 2,550 children ages 5 to 17 who were removed from their parents after crossing the U.S. southern border, more than 570 are still in the custody of the U.S. Department of Health and Human Services and in government shelters.

But of those cases, about 410 children have parents already outside of the United States, meaning they were likely deported without their child and are not able to be reunited with their children in the United States. Nearly 70 other children have parents who are still in America, but no contact has yet been made.

The remaining cases include parents who require further background checks, are affected by separate litigation or have supposedly waived reunification, although the ACLU has disputed that classification.

The government's filing, however, did not indicate how many reunited parents still in the U.S. are under final orders of removal, meaning they could be deported at any time with their children. As of a week ago, that number was at more than 1,000.

A separate class-action lawsuit filed last month in Washington seeks to stop the deportation of all children, and argues they have an independent right to seek asylum and to be accompanied by their parents while in those proceedings.

The HHS deferred to the DOJ for comment Friday.

The ACLU said in Thursday's filing that it "often takes a degree of detective work" as it tries to make contact with deported parents, who may be in hiding to avoid prosecution.

U.S. District Judge Dana Sabraw has ordered that all the migrant children still separated from their parents be reunited. A conference call was scheduled Friday with the ACLU and the Trump administration to discuss how to move forward.

"The administration is sitting on information that will allow the parties to find these parents," said ACLU's Gelerent.