LOS ANGELES — The federal judge overseeing the U.S. government's efforts to reunify more than 2,500 migrant children it separated from their parents ordered a temporary hold on deportations for reunified families on Monday.

Judge Dana Sabraw of the Southern District of California said the government must halt the deportations in response to a filing by the ACLU that claimed the government has refused to deny "that mass deportations may be carried out imminently and immediately upon reunification."

Lawyers from the ACLU had expressed concern that they would not be able to meet and represent families, many of whom make asylum claims, if they were quickly deported.

The government said last week that it had reunified all 57 eligible children under age 5 covered by Sabraw's original reunification order, excluding those whose parents had been deported or have criminal records, one day past Sabraw's initial reunification deadline for young children. Most of the parents reunited with young children were released with ankle monitors pending court hearings, according to government lawyers.

U.S. Health and Human Services now faces a July 26 deadline to reunify the remaining children, ages 5-17, and the ACLU worries many of those will be deported too quickly.

Government officials told Sabraw that 2,480 of the older children have been matched to a parent; 918 of those children's parents have been cleared by government agencies and are expected to be reunified by the July 26 deadline.

Sabraw will hear from the government and ACLU lawyers representing migrant parents separated from their children on July 23 and is expected to make a final decision on how quickly reunified families can be deported.

In its filing on Monday, the ACLU said Attorney General Jeff Sessions's new asylum guidelines will make it harder for the reunited families to claim asylum. Many parents have had to choose between deportation with their children or leaving their child in the U.S. with hopes that they would win their asylum case.

The ACLU had "assumed there would be sufficient time (at least a week) for parents to make this decision after reunifications occurred," lawyers for the advocacy group said in their court filing. "But that has apparently changed."

A flowchart provided by the government Sunday shows that the government "is contemplating that parents will be forced to make the choice whether to leave their children behind in advance of seeing their children," the ACLU filing said.

Click here to see the government's flowchart

Sabraw ordered Friday that the government give the ACLU a 12-hour notice before each reunification. The ACLU asked Sabraw to expand his order to include notification on which families are slated for deportation.

The government said that space in detention facilities may become an issue if it is not allowed to deport reunited families for a week. Sabraw said his decision to halt deportations should not be "unhinging reunifications underway."

"If space is an issue, the government will have to make space," Sabraw said.

Jacob Soboroff reported from Los Angeles, and Julia Ainsley from Washington, D.C.