Washington (CNN) The White House, facing mounting outcry and contradictory statements about President Donald Trump's practice of separating children from their parents at the US border, entered damage control mode on Monday.

Press secretary Sarah Sanders delayed her briefing almost four hours as Kirstjen Nielsen, the homeland security secretary, was flown back from New Orleans to face reporters. Originally scheduled for 1:15 p.m., the briefing was subsequently pushed to 3:30 p.m., then 4 p.m. and finally to 5 p.m.

The effort to put Nielsen in front of cameras to explain the policy reflected heated internal West Wing conversations and Trump's growing frustration that his own administration's practice is drawing ire and making him appear heartless.

Nielsen could offer an authoritative voice on the matter, Trump and other top officials believed, and she underwent extensive preparation ahead of the briefing.

Instead, the briefing devolved into a tense back-and-forth over the separation practice, which has dominated television news with images of children being kept in chain-link cages. Nielsen insisted there was little the President could do to end the practice, which she pinned on existing law. Her statements at times bent fact, including her claim that only Congress could end the separations.

The outcry over the President's immigration policy gained volume across the political spectrum ahead of a potentially consequential Capitol Hill meeting with Trump and Republican lawmakers scheduled for Tuesday.

Nielsen underwent briefing preparations three times on Monday afternoon: first with homeland security officials next door to the White House, again later in chief of staff John Kelly's office and once more with Sanders and the press team before facing reporters around 5:15 p.m. -- four hours after the briefing was initially scheduled to begin. White House deputy press secretary Raj Shah later claimed the White House asked Nielsen's office if she would be able to participate in the briefing.

Nielsen and Trump didn't discuss the separation issue one-on-one upon her return to Washington on Monday afternoon, a White House official said. But she sat in on an Oval Office meeting with the President and Republican Sens. Shelley Moore Capito and Richard Shelby to discuss border wall funding.

Trump was supportive of having Nielsen appear at the White House podium, people familiar with the matter said, believing she could offer a consistent message on the administration's practice. He has grown frustrated in recent days at the images of separated children playing out on television and the subsequent blame he's received.

One White House official said Sanders, who has faced credibility issues after weeks of misleading statements, was wary of answering questions along about the family separation issue. Sanders denied that she was hesitant about taking questions from reporters.

"I thought it was important for the secretary, and one of the primary experts on this process and the things that are going on, to come out here and have the chance to speak to you and for you guys to be able to ask questions directly of her and the leaders in this administration," Sanders said during the briefing Monday. "But I'm standing here in front of you."

But Sanders has been in the position of not wanting to be the lone figure speaking for the administration before.

After the staff secretary Rob Porter was accused by two ex-wives of physical abuse, Sanders read glowing statements defending Porter, but as the story unfolded, it became clear that Kelly and White House counsel Don McGahn knew more than they had initially claimed.

Sanders, frustrated with having initially defended Porter , engaged in a West Wing yelling match with McGahn, and refused to face reporters on the subject again if she didn't get answers. She implored both Kelly and McGahn to instead brief reporters. Though Kelly accepted, his briefing never materialized because it was canceled after a gunman opened fire on a south Florida high school.

Growing frustration

While the President has implored his aides to stanch the political fallout, he hasn't moved to end the humanitarian crisis itself.

Publicly, Trump has blamed Democrats for the catastrophe, saying that if they agreed to an immigration compromise the practice could be ended. Privately, Trump has demanded his staff find a way to better communicate what precisely his administration is doing that has resulted in children being held in cages, some erected in empty box stores, people familiar with the matter say.

After angrily watching television coverage of the detentions on Sunday and Monday -- including contradictory statements made by his aides -- Trump determined he needed to act as his own spokesman during a morning event in the East Room, the people said.

He and policy staffer Stephen Miller together sketched out a forceful three-minute opening to a speech otherwise focused on space policy, an official said. Trump arrived at the event more than 30 minutes late, intent on cleaning up what has become a deepening problem for his administration.

Unlike past instances when Trump's toughest rhetoric came during moments of improvisation, his words on Monday were not ad-libbed.

"The United States will not be a migrant camp, and it will not be a refugee holding facility," he said, reading from a paper with prepared remarks. "A country without borders is not a country at all. We need borders. We need security. We need safety. We have to take care of our people."

The statement, which drew applause from some in the audience of aerospace executives but stoned-face silence from others, offered little conciliation for the outraged Democrats and some Republicans who have decried the family separation policy. Instead, it was more evidence of Trump's long-standing habit of entrenching at his most contentious moments, giving little to his critics in the hopes of invigorating his supporters.

Unapologetic stance

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Indeed, a CNN poll released Monday showed a majority of Republicans -- 58% -- approve of Trump's family separation practice, even as two-thirds of Americans overall disapprove of it. The CNN survey was conducted June 14-17 by SSRS.

Trump's unapologetic remarks came after a weekend of confusing statements from members of his administration. Nielsen had tweeted: "We do not have a policy of separating families at the border," a misleading statement that also contradicted other Trump officials speaking the same day.

Kellyanne Conway, the President's counselor, said on NBC that "as a mother, as a Catholic, as somebody who has a conscience ... I will tell you that nobody likes this policy."

And Miller, an immigration hardliner who has helped craft some of the President's toughest policies, told The New York Times : "It was a simple decision by the administration to have a zero-tolerance policy for illegal entry, period."

The diversity of official viewpoints led to an impression the administration was floundering amid intense criticism of the separations. The outcry included statements from all four living former first ladies, led by Laura Bush , the wife of Republican former President George W. Bush.

Asked to respond to the criticism from Bush, Nielsen brushed over the substance of the critique, saying: "Calling attention to this matter is important."

The contradictory stances from the White House come amid a tenuous relationship between the President and his Department of Homeland Security secretary. Trump recently blew up at Nielsen during a lengthy tirade in a Cabinet meeting focused on immigration, grumbling in front of others that she wasn't doing enough to secure the border, CNN reported at the time.

Several officials inside the administration have raised the question of why it is Nielsen who is being targeted so fiercely by critics instead of Attorney General Jeff Sessions, who publicly announced the zero-tolerance policy. Sessions is also not in good standing with Trump over his decision to recuse himself from the Russia investigation.

Earlier Monday, aides attempted to present a more cohesive message. Nielsen, speaking at the National Sheriffs' Association annual conference in New Orleans, coordinated her message with the White House beforehand, an official told CNN, making clear the administration is attempting to get on the same page as the outrage grows.

"We will not apologize for the job we do," she said. "It is important to note these minors are very well taken care of. Don't believe the press."

The unapologetic stance aside, many in the White House have felt increasingly uncomfortable with the separation practice amid mounting scrutiny and a wave of negative headlines. One White House aide said the intense focus on family separation could put strain on immigration talks in the House, which Trump will attempt to facilitate on Tuesday when he heads to Capitol Hill and faces the GOP conference.

"It sucks. Nobody likes it," the aide said of the family separations.

Messaging split

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An administration official said the White House's messaging is split between officials -- including Trump himself -- who are blaming Democrats for the policy and officials who are embracing it as part of the President's immigration agenda.

A source close to the White House said many of Trump's outside advisers are unhappy with his decision to point the finger at Democrats rather than own a policy shift that could be presented as the fulfillment of a campaign promise. The source and other outside advisers have tried to relay to him that blaming his political opponents sends the "totally wrong message" about his policy -- particularly because it's an inaccurate statement that gives critics of the practice an obvious way to undermine it.

"It gives them ammunition and it looks like we're hiding or equivocating," the source said. "The President has made it harder."

Many Republicans in Congress are skeptical that Trump's trip to Capitol Hill this week will ease the passage of an immigration bill the White House has characterized as a compromise.

"I don't think it'll move the needle much," a senior GOP congressional aide said of Trump's upcoming visit with the conference.

Marc Short, Trump's legislative director, and other legislative aides plan to meet with the President several times Monday and Tuesday to prepare him for his meeting with House Republicans, a White House aide said. The meeting will likely include efforts to prepare Trump for questions he may face from members upset about family separation, the White House aide added.