Trump's tweets came a day after he ratcheted up his attacks on the group of freshman lawmakers tweeting that "'Progressive' Democrat Congresswomen" should stop criticizing the government and "go back" to where they came from.
Without naming the lawmakers, the president appeared to be referring to what has come to be known as a "squad" of progressive freshman women of color, which includes Reps. Alexandria Ocasio-Cortez, D-N.Y., Ilhan Omar, D-Minn., Rashida Tlaib, D-Mich., and Ayanna Pressley, D-Mass. The quartet held a news conference on Monday afternoon at the Capitol to respond to the president's attacks and refused to get down in the muck. Instead they sent a clear message: don't fall for it.
"I encourage the American people and all of us in this room and beyond to not take the bait," Pressley said in her opening remarks. "This is a disruptive distraction from the issues of care, concern and consequence to the American people."
"We are more than four people," Pressley added. "We ran on a mandate to advocate for and represent those ignored, left out and left behind. Our squad is big. Our squad includes any person committed to building a more equitable and just world and that is the work that we want to get back to. And given the size of this squad and this great nation, we cannot, we will not be silenced."
Omar called the Trump administration "the most corrupt administration in our history" and asserted that the president's agenda "is the agenda of white nationalists."
"This is a president who has openly violated the very value our country appears to uphold. Equality under the law, religious liberty, equal protection, and protection from persecution. And to distract from that, he's launching a blatantly racist attack on four duly elected members of the United States of House of Representatives, all of whom are women of color. It is time for us to stop allowing this president to make a mockery out of our constitution. It is time for us to impeach this president," she said.
Ocasio-Cortez had a message for American children, "No matter what the president says, this country belongs to you and it belongs to everyone."
While they denounced Trump's comments over and over again, the four congresswomen directed their remarks back to the president's policies.
"We'll stay focused on our agenda and we won't get caught slipping," Ocasio-Cortez said. "Because all of this is a distraction. It is a distraction from what is most important and from our core values as American citizens."
Tlaib said the president's attacks are "simply a continuation of his racist and xenophobic playbook."
"Sadly, this is not the first, nor will it be the last time we hear disgusting, bigoted language from this president. We know this is who he is," she added.
"I believe this is a pivotal moment in our country. The eyes of history is watching us," Omar added.
While the congresswomen were speaking, the president was posting messages to Twitter.
"We will never be a Socialist or Communist Country. IF YOU ARE NOT HAPPY HERE, YOU CAN LEAVE! It is your choice, and your choice alone. This is about love for America. Certain people HATE our Country...." he wrote.
With the president on Monday claiming that many people "agree" with him, Pressley said it was "in contradiction to the experience that I have every day, including in the airport on my way here."
"There were many people who approached me and who said, I disagree with some of your policies, I'm an independent, I'm a Republican and I think what he did was wrong," Pressley recounted. "And he won't apologize. But I am going to apologize. So I have experienced nothing in the wake of those comments. Again, but words of denouncing these xenophobic, bigoted words."
On Monday night, Democrats introduced a resolution condemning Trump for his comments on Sunday. A vote on the bill could come as early as tomorrow.
At an event at the White House on Monday afternoon, Trump was asked which congresswomen he was referring to in his tweets, and he said, "You can guess."
Ocasio-Cortez responded on Twitter Monday morning saying that his comments are "hallmark language of white supremacists."
"It's important to note that the President's words today, telling four American Congresswomen of color "go back to your own country," is hallmark language of white supremacists. Trump feels comfortable leading the GOP into outright racism, and that should concern all Americans," Ocasio-Cortez tweeted.
The president said to reporters that his remarks where "not at all" racist, adding "if you're not happy here, then you can leave."
"Do you think those Democratic women are not American," ABC News senior White House Correspondent Cecilia Vega asked Trump Monday afternoon.
He replied, "If somebody has a problem with our country, if someone doesn't want to be in our country they should leave. That's all."
Trump was also asked by reporters if he is concerned that many people have viewed his tweets as racist and that white nationalist groups are finding common ground with him.
"It doesn't concern me because many people agree with me, and all I'm saying, they want to leave, they can leave now," Trump responded. "It doesn't say leave forever. It says leave."
Coming to the president's defense on Monday was Andrew Anglin, founder of the neo-Nazi news site, The Daily Stormer.
"This is the kind of WHITE NATIONALISM we elected him for," Anglin said.
"This is what elected Trump and this is what will always be the best way for him to gain support," he added.
Trump's comments have been widely criticized by Democratic lawmakers, many who have characterized his attacks as racist.
The president's tweets follow a week of contention between the freshman lawmakers and House Speaker Nancy Pelosi.
"I reject @realDonaldTrump's xenophobic comments meant to divide our nation," Pelosi tweeted on Sunday morning.
"When @realDonaldTrump tells four American Congresswomen to go back to their countries, he reaffirms his plan to "Make America Great Again" has always been about making America white again. Our diversity is our strength and our unity is our power," Pelosi added coming to the defense of the lawmakers despite recent public disagreements.
Top Republicans in Congress had been largely silent on the attacks, but more were speaking out on Monday.
In an interview with the anchors of Fox & Friends on Monday morning, Sen. Lindsey Graham, a Trump ally, justified the president's attacks on those four freshman congresswomen by branding them as "a bunch of Communists" who "hate Israel" and "hate our own country."
"We all know AOC and this crowd are a bunch of communists they hate Israel, they hate our own country," Graham said. "I think they're American citizens duly-elected running on an agenda that is disgusting, that the American people will reject."
Later Monday morning, Rep. Paul Mitchell, R-Mich., responded to the president on Twitter, writing that "we must be better than comments like these."
Sen. Susan Collins, R-Maine, released a statement Monday afternoon saying that Trump's tweets were "way over the line."
"I disagree strongly with many of the views and comments of some of the far-left members of the House Democratic Caucus -- especially when it comes to their views on socialism, their anti-Semitic rhetoric, and their negative comments about law enforcement -- but the President's tweet that some Members of Congress should go back to the 'places from which they came' was way over the line, and he should take that down," Collins said.
British Prime Minister Theresa May and Canadian Prime Minister Justin Trudeau have also weighed in.
"The language that was used to refer to these women was completely unacceptable," May told CNN on Monday morning.
Trudeau told CBC News Network, "That's not how we do things in Canada."
He added, "Canadians and indeed people around the world know exactly what I think about those particular comments."
ABC News' Meridith McGraw contributed to this report.