What's happening at the US border

Former Homeland Security Secretary John Kelly, who is now White House chief of staff, told CNN's Wolf Blizter in March 2017 that the department was considering separating undocumented children from their parents at the border.

Kelly said he was considering any policy that would help deter "people from Central America to getting on this very, very dangerous network that brings them up through Mexico into the United States."

"We have tremendous experience of dealing with unaccompanied minors," he told Blitzer. "We turn them over to (Health and Human Services) and they do a very, very good job of putting them in foster care or linking them up with parents or family members in the United States."

He continued: "Yes I'm considering (that), in order to deter more movement along this terribly dangerous network. I am considering exactly that. They will be well cared for as we deal with their parents. ... It's more important to me, Wolf, to try to keep people off of this awful network."

Why we're talking about this now

Current Homeland Security Kirstjen Nielsen is facing scrutiny for the policy resulted in an uptick of children being separated from their families. Today, she said the "vast majority" of children being held in the detention facilities were sent to the US alone by their parents.

Homeland Security Secretary Kirstjen Nielsen was asked if the children who have been separated from the parents were also being used as pawns to against a border wall.

Nielsen denied the children were being used in any way.

"The children are not being used as a pawn and we're trying to protect the children which is why I'm asking Congress to act," she said. 

Asked Monday why the administration's policy of separating children from their parents on the border isn't "child abuse," Homeland Security Secretary Kirstjen Nielsen insisted conditions at the detention facilities are up to par.

Here's what she told CNN's Jeff Zeleny:

She said the "vast majority" of children being held in the detention facilities were sent to the US alone by their parents.

What the American Academy of Pediatrics says:

Dr. Colleen Kraft, president of the American Academy of Pediatrics, said removing children from the care of their parents at the border amounts to a form of child abuse.

"This is not normal activity or brain development with these children. The takeaway is that these children need their parents," she said. "This does amount to child abuse."

Department of Homeland Security Secretary Kirstjen Nielsen continued to defend the Trump administration's highly scrutinized immigration policy at a White House press briefing Monday while at the same time calling on Congress to change the law.

"Congress and the courts created this problem and Congress alone can fix it," she said at today's press briefing. "Until then, we will enforce every law we have on the books to defend the sovereignty and security of the United States."

She later added, "Surely it is the beginning of the unraveling of the democracy when the body who makes the laws, instead of changing them, tells the enforcement body not to enforce the law. I ask Congress to act this week so that we could secure our borders and uphold our humanitarian ideals."

President Trump has squarely -- and misleadingly -- blamed Democrats for the unfolding crisis.

Rep. Steve Stivers, the chair of the Republican National Campaign Committee, came out against the Trump administration policy of splitting up families at the border on Monday.

“As a father, I know firsthand that there is nothing more important than family, and I understand why kids need to be with their parents," he wrote in a Facebook post.

“I am writing a letter to understand the current policies and to ask the Administration to stop needlessly separating children from their parents. If the policy is not changed, I will support other means to stop unnecessary separation of children from their parents,” he added.

This could be taken as a signal to vulnerable Republicans in the House that it is ok to break with Trump in this issue.

Homeland Security head Kristjen Nielsen is speaking at the White House press briefing, and she's expected to take questions.

Watch live on CNNGo, and follow here for highlights.

No, as internal Department of Homeland Security documents obtained by CNN show.

Administration officials predicted the zero-tolerance policy would deter immigrants from trying to enter the United States illegally. Instead, publicly released data showed a roughly 5% uptick in the number of people caught crossing the border illegally in May when compared to figures from April, including a big jump in unaccompanied children.

— From CNN's Catherine E. Shoichet

Most are taken to facilities run by the Department of Health and Human Services' Office of Refugee Resettlement. These facilities were originally set up to house unaccompanied minors -- children who crossed the border without parents or legal guardians.

As a result of the administration's new policy, these so-called shelters are also increasingly housing children who crossed the border with their parents and were subsequently separated from them.

Currently there are a total of more than 11,700 children in the office's custody, according to officials.

Immigrant rights organizations say holding children in such facilities -- especially children who were taken from their parents -- is cruel and inhumane. Officials have categorically denied such accusations, characterizing them as misleading reports from advocacy groups and media outlets.

"It is important to note that these minors are very well taken care of. Don't believe the press. ... We operate according to some of the very highest standards in the country," Homeland Security chief Kirstjen Nielsen said Monday.

— From CNN's Catherine E. Shoichet

A White House official tells CNN that Sarah Sanders did not want to do the press briefing today amid a swirl of questions about the separation policy, so Homeland Security chief Nielsen is being flown back from New Orleans to take questions.

This explains the repeated delay for today's White House press briefing. It’s an open question whether Nielsen will make it back by 5 p.m. ET.