WASHINGTON--President Donald Trump and top members of his administration pushed back Monday against a cavalcade of criticism from Republicans, including some prominent White House allies, of a border policy that has led to the detention of immigrant parents and their children at separate facilities.

The White House narrative, articulated in different settings by Trump, Homeland Security Secretary Kirstjen Nielsen, Attorney General Jeff Sessions and others, was that Democrats were at fault for a pre-existing framework of laws and policies, including an Obama-era detention waiver for families, that the administration says has encouraged immigrants to fraudulently claim familial relations.

In fact, the separation policy is a direct result of the Trump administration's decision to implement a "zero-tolerance" policy at the border, and the White House has not been able to demonstrate any Democratic policies that created it. Nonetheless, the president and his top aides continue to insist that fraudulent family claims have led to human-trafficking enterprises and other criminal activities, though have produced little evidence to that effect.

"The United States will not be a migrant camp and it will not be a refugee holding facility ... not on my watch," Trump said at the White House Monday. "Immigration is the fault, and all the problems that we’re having because we cannot get them to sign legislation, we cannot get them even to the negotiating table, and I say it’s very strongly the Democrats' fault."

"What's happening is so sad. It's so sad," he said.

Nielsen said at a White House press briefing late Monday that until Congress takes action, "we will enforce every law we have on the books."

Sen. Dianne Feinstein, D-Calif., has introduced legislation that would end family separations at the border. Rep. Mike Coffman, R-Colo., who is facing one of the toughest re-election battles in the country, said Monday that he would be willing to bring up a companion measure in the House. And Republican Sen. Ted Cruz, a Texan who is normally a loyal supporter of the president, said Monday he would introduce a bill that would create temporary facilities to keep families together while cases are being adjudicated and expedite consideration of asylum requests.

Democrats have accused Trump of using children separated from their families as leverage to pass the rest of his immigration agenda. Nielsen said the kids were not being used as "pawns" in a political game.

An official at the Department of Health and Human Services told NBC News that there are 11,785 minors in its care as of Monday, a figure that includes "all minors at shelters and facilities in the unaccompanied alien children program."

In just the last four days, 810 children have been taken in, and, at the current pace, the number of migrant kids being held by HHS would hit 20,695 by Aug. 1.

All four living former first ladies condemn Trump border policy

All four living former first ladies, Rosalynn Carter, Hillary Clinton, Laura Bush and Michelle Obama, have stepped out of political retirement to condemn the Trump administration's practice of separating parents and children at the border.

Speaking at a women's group in New York City on Monday, Clinton called family separation "an affront to our values" and said she had warned Trump's immigration policy would lead to this during her 2016 presidential campaign against him.

Clinton, a practicing Methodist since her childhood, also slammed the administration's religious justifications for the practice."

"Those who selectively use the Bible to justify this cruelty are ignoring a central tenant of Christianity," the former first lady said. "These policies are not rooted in religion. What is being done using the name of religion is contrary to everything I was ever taught."

She added, "Jesus Christ said, 'Suffer the little children unto me' not 'let the little children suffer.'"

Meanwhile, Bush, who almost never speaks out on political issues, broke partisan ranks in a Washington Post op-ed.

“I live in a border state. I appreciate the need to enforce and protect our international boundaries, but this zero-tolerance policy is cruel. It is immoral. And it breaks my heart,” she wrote.

In her op-ed article, Bush appealed to Americans’ sense of morality and painted the policy as a dark stain on the nation’s history that she compared to the HIV/AIDS crisis and Japanese internment. "These images are eerily reminiscent of the Japanese-American internment camps of World War II, now considered to have been one of the most shameful episodes in U.S. history. We also know that this treatment inflicts trauma; interned Japanese have been two times as likely to suffer cardiovascular disease or die prematurely than those who were not interned," she wrote.

Rosalynn Carter called the policy of separating families "disgraceful and a shame to our country."

Michelle Obama also weighed in to support Bush.

The current first lady, Melania Trump, commented over the weekend on what's happening at the border, pushing for bipartisan cooperation to end the separation of migrant children from their parents at the border.

"Mrs. Trump hates to see children separated from their families and hopes both sides of the aisle can finally come together to achieve successful immigration reform," according to a statement from her spokeswoman. "She believes we need to be a country that follows all laws, but also a country that governs with heart."

Metal wire, mylar blankets: This is what a 'zero tolerance' border policy looks like

McALLEN, Texas--Hundreds of young migrants are being kept behind metal wire, the type you’d see on a neighborhood batting cage or a dog kennel, inside the country’s largest immigration processing center.

A total of 1,174 children have been taken away from their mothers and fathers in the Border Patrol’s South Texas Rio Grande Valley sector, with many brought to the Central Processing Station in McAllen, Texas, since the policy was announced on May 7, according to Manuel Padilla, the Border Patrol sector chief.

NBC News was part of a group that went behind Ursula's highly secured doors Sunday to see firsthand what migrants go through before separations occur.

From Ursula, children will be sent to separate facilities run by the Department of Health and Human Services while their parents are sent to a detention center to await prosecution before a federal judge.

U.S. policy dictates that no one of any age should be kept in one of these processing centers longer than 72 hours. But because of the backlog at HHS centers for children, hundreds of minors are forced to stay past that limit.

Cameras were not permitted on the Father's Day tour, but the Border Patrol provided handout images of the stark situation: 1,129 migrants were detained in the 77,000-square-foot facility, nearly all of them behind the metal wire.

Mylar blankets, the type marathon runners wrap themselves in after finishing a race, covered the bodies of migrants throughout as they lay on mattresses atop concrete floors.

In the 55,000-square-feet of the facility dedicated to families and unaccompanied minors, detainees were sorted based on age, gender and family status into what the Border Patrol called four pods: one for girls 17 and under, another for boys 17 and under, mothers with children and fathers with children.

Parents who are separated from their children aren’t taken away until they are brought into processing to leave the facility, only at that moment do they find out if they’ll be prosecuted, instead of taken to an ICE detention center with their children. They receive what is called a “tear sheet” informing them of their fate and how they might find their children again.

Only four social workers were on hand to care for the hundreds of children, a backup system when Border Patrol agents are not prepared or qualified to deal with the challenges that come with caring for a child.

Some children who arrived with parents now find themselves alone in the facility before they are picked up and taken into the custody of the HHS, which cares for unaccompanied migrant children. Others arrived on their own.

Trump admin discussed separating moms, kids to deter asylum-seekers in Feb. 2017

WASHINGTON--The idea of separating migrant children from their mothers was discussed during the earliest days of the Trump administration as a way to deter asylum-seekers, according to notes from a closed-door DHS meeting.

Notes from a town hall held for Citizenship and Immigration Services asylum officers on Feb. 2, 2017, show that the agency's asylum chief, John Lafferty, told the officers they might have to "hold mothers longer" and "hold children in HHR/ORR," an acronym for facilities for children run by HHS. (Source: NBC News)

Story Date: June 19, 2018