Administration officials have defended the tactic as necessary to secure the border and suggested it would act as a deterrent to illegal immigration - which Trump has long made a key goal of his presidency.
"I hate the children being taken away", Trump said Friday morning.
"We don't want what is happening with immigration in Europe to happen with us!"
In recent years, we've heard a lot of the argument that "If we don't have borders, we don't have a country".
South Florida Democratic members of Congress have blasted the administration and its policy.
President Trump continues to falsely blame Democrats for these actions, despite the fact that there is no US law that requires the separation of families and senators on both sides of the aisle have spoken out against the "zero-tolerance" policy. "Where is the outcry for the killings and crime being caused by gangs and thugs, including MS-13, coming into our country illegally?" "We are enforcing the laws passed by Congress", she said in an appearance before the National Sheriffs' Association in New Orleans.
"What we're doing as a nation is inflicting enormous harm on these kids and on the parents when it's totally unnecessary during this time when they're waiting for their asylum hearing", said Sen.
"Now as we watch with broken hearts, that's exactly what's happening", she said.
Almost 2,000 immigrant children were separated from parents over a period of about six weeks in April and May, according to the Department of Homeland Security. He added the White House does not "want" to separate children from their parents and that the United States is "dedicated to caring for those children".
Speaking at a women's forum award ceremony on Monday, Clinton also said Trump's claim that the Democrats were to blame for the separations was an "outright lie".
A spokeswoman for Melania Trump told CNN on Sunday that the first lady "hates to see children separated from their families" and hopes lawmakers from both parties can agree on immigration reform. But she believes the zero-tolerance policy is cruel and immoral. "I visited Thailand and witnessed firsthand the trauma of parents and children separated by circumstances beyond their control", the statement said.
The family separations are the result of Mr Trump's "zero tolerance" policy that arrests all adults who are caught trying to enter the United States illegally, including those seeking asylum.
"If you cross the border unlawfully, even a first offense, we're going to prosecute you". She compared the separation of the children to the internment camps for Japanese-Americans in World War II.
Susan Collins, a Republican senator from ME, called the practice "contrary to our values in this country" and said it was "traumatizing" to the children who are caught in the center of an already polarizing debate over immigration in Washington.
The President is refusing to sign any new immigration legislation that doesn't include funding for his promised border wall. Religious groups, including some conservative ones, are protesting.
Trump was due to meet with Republicans in the House of Representatives on Tuesday as they prepared to vote on two immigration bills.