Washington (CNN) President Donald Trump amplified his heated immigration rhetoric on Tuesday, accusing Democrats of wanting migrants to "infest our country" and turning a speech on the economy into an angry tirade defending his harsh stance.

It was a reflection of Trump's growing frustration that the family separation crisis roiling his administration has led to accusations of child abuse and heartlessness. Privately, Trump has insisted he is right to push forward with a practice that has drawn outcry from across the political spectrum.

In a morning tweet, Trump used language evoking images of pests, not human beings, when describing migrants approaching the US border.

"Democrats are the problem," he wrote. "They don't care about crime and want illegal immigrants, no matter how bad they may be, to pour into and infest our Country, like MS-13. They can't win on their terrible policies, so they view them as potential voters!" he wrote.

Democrats are the problem. They don't care about crime and want illegal immigrants, no matter how bad they may be, to pour into and infest our Country, like MS-13. They can't win on their terrible policies, so they view them as potential voters!

Later, he declared during remarks at a hotel that he had no choice but to remove children from their parents at the border.

"When you prosecute the parents for coming in illegally, which should happen, you have to take the children away," he said. "Now, we don't have to prosecute them, but then we're not prosecuting them for coming in illegally. That's not good."

It was a defiant stance amid growing outrage at the family separations. Democrats and some Republicans have decried the practice as cruel, citing images of children being detained inside chain-link cages, some erected inside empty box stores.

But Trump and his aides have staunchly insisted they have no choice, instead blaming Democrats for not supporting legislation that would allow the practice to end.

That's a false claim; The family separations are a result of the administration's "no tolerance" immigration policy. But Trump reiterated the accusation on Tuesday.

Speaking at the small business event in Washington, the President said the separation policy is "a result of Democrat supported loopholes in our federal laws" that he said could be easily changed.

"These are crippling loopholes that cause family separation, which we don't want," Trump said.

At the same time, the President appeared to suggest the practice could act as a deterrent for future migrants considering entering the US with their children.

"We want a great country. We want a country with heart. But when people come up, they have to know they can't get in," he said. "Otherwise it's never going to stop."

And he declared the US needs to be secured, whether or not that seems politically palatable.

"You have to stand for something and you have to stand for safety and security of our country. We can't let people pour in," he said. "Maybe it's politically correct or maybe it's not. We've got to stop separation of the families, but politically correct or not, we have a country that needs security, that needs safety, that has to be protected."

The President's entrenchment amid a loud uproar comes amid a developing humanitarian -- and political -- crisis on the United States' border with Mexico, where at least 2,000 children have been separated from their parents as a result of the administration's policy.

Last month, the administration publicly announced its decision to charge every adult caught crossing the border illegally with federal crimes, as opposed to referring those with children mainly to immigration courts, as previous administrations did.

Because the government is charging the parents in the criminal justice system, children are separated from them with no clear procedure for their reunification aside from hotlines the parents can call to try to track their children down.

In the past weeks, heartbreaking images and audio of children crying for their parents have captured the nation's attention as lawmakers seek to find a solution to end the separations and the White House doubles down on its insistence that it is simply enforcing the law.

On Tuesday, Trump is due to meet with congressional Republicans to discuss options for immigration legislation that might bring the practice to an end. But a path forward is unclear, and Trump himself suggested on Tuesday he'd likely make changes to whatever is passed.

"We have one chance to get it right. We might as well get it right, or let's just keep it going," he said.

White House and congressional officials said Trump was referring to family separation language that GOP leadership plans to add to a compromise immigration bill when he referenced making "changes" to the legislation.

Trump's hardline immigration rhetoric was a central piece of his campaign rallying cries, beginning with his campaign announcement speech in June 2015.

"When Mexico sends its people, they're not sending their best ... They're sending people that have lots of problems, and they're bringing those problems with us. They're bringing drugs. They're bringing crime. They're rapists. And some, I assume, are good people," Trump said at the time.

On Tuesday, he revived his assertion that some countries are not sending their "best," and threatened to withdraw US aid.

"When countries abuse us by sending people up -- not their best -- we're not going to give any more aid to those countries," he said. "Why should we?"