"Trump has made it clear that he's going to secure America's border at all cost and this rule plays a vital role in the strategy to restore the integrity to our immigration system and our national security", an unnamed senior administration official told The Washington Times, while giving a preview of the announcement.
Immigrant advocates, in contrast, said they believed the change would put many more immigrants into detained court proceedings, slowing the process and keeping children locked up for longer.
The Trump administration on Wednesday announced plans to end a decades-old settlement agreement that had set a 20-day limit for holding children and issue new regulations that could hold undocumented families detained together indefinitely.
The rule, which is certain to draw a legal challenge, would replace a 1997 court settlement that limits the amount of time US immigration authorities can detain migrant children. Once the rule takes effect, officials said, they hope to complete migrants' initial immigration proceedings within two months, which is triple the time children are held now.
On July 15 the administration unveiled a rule to bar nearly all immigrants from applying for asylum at the southern border, and on August 12 it announced regulation denying visas and permanent residency for those who fail to make enough money.
The regulations are expected to be formally published Saturday and go into effect in 60 days absent legal challenges.
Under the new rule, the administration would be free to send families who are caught crossing the border illegally to a family residential center to be held for as long as it takes for their immigration cases to be decided. The settlement has for 22 years governed the treatment of migrant children in US custody, requiring government agencies to follow a detailed set of standards while caring for children apprehended by immigration and border agents.
But Ken Cuccinelli, the administration's acting director of the Citizenship and Immigration Services, lauded family detention and the new rule, calling today "Flores Day" in a video posted to Twitter.
Congressman Joaquin Castro, the chairman of the Congressional Hispanic Caucus, said in a statement that the administration is "punishing vulnerable families".
The Flores Settlement Agreement generally compels the USA government to move children from austere border jails into licensed, child-appropriate facilities as expeditiously as possible.
The massive influx of Central American families to the U.S. -Mexico border has vastly strained the system, though agreements by Mexico to clamp down on migrants heading north and a new agreement with Guatemala forcing migrants to claim asylum there instead of heading north are expected to reduce the flow, though the action has been decried as inhumane.
The government operates three family detention centres that can hold a total of about 3,000 people.
According to government data, more migrants were deported during Obama's eight years in office than under any previous administration, which earned him the unfortunate moniker of 'deporter-in-chief.' During his first term, almost 400,000 people were sent back per year, topping out in 2012 at over 409,000. The number of individuals within family units who Border Patrol has apprehended along the southern border so far this fiscal year reached more than 390,000 by the end of June.
"No child should be a pawn", McAleenan said at a news conference announcing the rule.
"Thousands of kids separated from their parents". That agreement is generally interpreted as meaning families must be released within 20 days. Children cared for toddlers, the lawyers said, adding that they had inadequate food, water and sanitation.