"We are pleased that the president is calling a halt to his inhumane and heartless policy of separating parents from their children", said Peter Schey, the lawyer in a lawsuit that resulted in a key agreement governing the treatment of migrant children in detention called the Flores settlement.
He said his order would not end the "zero-tolerance" policy that criminally prosecutes all adults caught crossing the border illegally. Experts have said such separation from parents can cause permanent emotional damage.
It remains unclear what will happen with the more than 2,300 children separated from their parents at the border in recent weeks.
The moves come as the House of Representatives prepares to vote Thursday on a pair of immigration bills that address the separations, as well as other issues that have divided the country's major political parties.
A separate case by the American Civil Liberties Union challenging family separations - but not the "zero tolerance" policy - argues that families have the right to remain unified.
Pelosi was quick to highlight the partisan nature of the debate, saying she's had no conversations with House Speaker Paul RyanPaul Davis RyanTrump backs down in rare reversal Trump, GOP launch full-court press on compromise immigration measure Meadows gets heated with Ryan on House floor MORE (R-Wis.) about a legislative solution to the separation of families at the southern border with Mexico - an issue that has risen to the forefront of an immigration debate that was initially focused on rescuing the Deferred Action for Childhood Arrivals (DACA) program.
Nielsen traveled to Capitol Hill Wednesday afternoon to brief lawmakers.
Two people close to Homeland Security Secretary Nielsen said early Wednesday that she was the driving force behind the plan to keep families together after they are detained crossing the border illegally.More news: Trump escalates trade war with new tariff threat against China
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'We don't like to see families separated.
De Blasio told reporters the children at Harlem's Cayuga Center included a 9-year-old Honduran boy sent to the center 2,000 miles by bus after being detained at the border. One White House official said Mrs. Trump had been making her opinion known to the president for some time that she felt he needed to do all he could to help families stay together, whether by working with Congress or acting on his own.
Business and religious leaders, four former US first ladies and Trump's wife, Melania Trump, also voiced sharp criticism of the policy to split up migrant families, many of them escaping poverty and turmoil in Central America, as they illegally crossed the USA border.
U.S. Attorney General Jeff Sessions speaks at the National Sheriffs' Association convention in New Orleans, Monday, June 18, 2018. Also, Secretary of Defense Jim Mattis and the heads of other agencies are ordered to find or construct facilities to house the detained families. The decision to cease prosecutions of parents with children was made by the Department of Homeland Security for logistical purposes because the official said it would not be "feasible" to bring children to federal courtrooms while their parents go before a judge.
Top CBP officials did not know what the executive order would ask them to do until its release Wednesday, the official said.
Immigrant children, who have been separated from their families under a now reversed policy by the Trump administration, are being housed in tents next to the Mexican border, in Tornillo, Texas, June 18, 2018.
"The U.S. authorities create different files for the children than for the parents, and it's very hard to follow up on those cases", Torres said.