The order follows an outcry from Republican and Democratic lawmakers, human rights advocates, religious leaders and others over stories and images of migrant children being taken from their parents and detained, sometimes in metal cages.
The Trump administration still faces legal challenges because of a court order that put a 20-day cap on how long immigration authorities may detain minors, and trigger fresh criticism of Trump's hardline immigration policies, which were central to his 2016 election campaign and now his presidency.
USA public opinion appears divided along partisan lines on the family separations, with two-thirds of all voters opposed, but 55 percent of Republicans supporting the policy, according to a Quinnipiac University National Poll.
"So we're talking about children in some cases who literately can't even communicate, have no idea what's happening to them, no ability to be in touch with their families", he said.
Videos of youngsters in cages and an audiotape of wailing children have sparked anger from United States groups ranging from clergy to influential business leaders, as well as condemnation from overseas, including Pope Francis.
"I'll be signing something in a little while that's going to do that", Trump told reporters.
Correa added that while Trump acknowledged the separation program hasn't been good policy, he also continued to blame Congress for a problem he instigated when he shifted policy in May. I feel very strongly about it.
On May 7, Sessions discussed the "zero-tolerance" policy for illegal entry on the southwest border. Instinctively combative and fond of chaos, Trump usually digs in on controversial policies, rather than backing down. Just in the past few days he had insisted his hands were tied by law on the issue of family separations even though his administration implemented a "zero tolerance" policy.
"Tomorrow the House will vote on legislation to keep families together". The ruling bars the government from keeping children in detention for more than 20 days.
Pratheepan Gulasekaram, an immigration law professor at Santa Clara University, said the Los Angeles federal court with jurisdiction over the Flores settlement is unlikely to grant the government's request to modify it.
"This is not a policy that people are excited about", he said. In reality, the Trump administration chose to separate families by criminally prosecuting parents.
"This executive order would replace one crisis for another".
It is not immediately clear whether, or when, detained children will be reunited with their parents.
Laura Bush said the detention centres reminded her of internment camps where Japanese-Americans were held during the Second World War. Those children have been placed in the custody of the Office of Refugee Resettlement under the Department of Health and Human Services, which manages care for unaccompanied minors.
Homeland Security secretary Kirstjen Nielsen is understood to be drafting an order to end the practice of separating children from their parents when they arrive at the border without papers.
The Republican-controlled U.S. Congress is considering legislation to address the issue.
Republicans said they were uncertain if either House measure would have enough votes to pass.
Attorney General Jeff Sessions is considering using DNA tests to verify the relationship between children and adults who illegally cross the border.