President Trump said on Twitter Sunday that "'Progressive' Democratic Congresswomen" should "go back" to their countries — even though three of the four lawmakers he was seemingly referring to were born in the U.S. and all are American citizens. His tweets drew disgust from House Democrats, who called them racist and xenophobic.

"So interesting to see 'Progressive' Democrat Congresswomen, who originally came from countries whose governments are a complete and total catastrophe, the worst, most corrupt and inept anywhere in the world (if they even have a functioning government at all), now loudly ... and viciously telling the people of the United States, the greatest and most powerful Nation on earth, how our government is to be run," he tweeted Sunday morning.

"Why don't they go back and help fix the totally broken and crime infested places from which they came. Then come back and show us how ... it is done," the president wrote. "These places need your help badly, you can't leave fast enough. I'm sure that Nancy Pelosi would be very happy to quickly work out free travel arrangements!"

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Mr. Trump was almost certainly referring to a quartet of newly elected non-white Democratic congresswomen who have been outspoken critics of the president and his administration. Three of those lawmakers — New York Rep. Alexandria Ocasio-Cortez, Michigan Rep. Rashida Tlaib and Massachusetts Rep. Ayanna Pressley — were born and raised in the U.S. The fourth, Minnesota Rep. Ilhan Omar, came to the U.S. from Somalia when she was 10 and became a citizen when she was 17.

All four women, who have come to be known as "the Squad," broke ethnic and gender barriers when they were elected last year. Omar and Tlaib are the first two Muslim women to serve in Congress. Pressley is the first black congresswoman to represent Massachusetts. Ocasio-Cortez, at 29, became the youngest woman ever elected to Congress.

So interesting to see “Progressive” Democrat Congresswomen, who originally came from countries whose governments are a complete and total catastrophe, the worst, most corrupt and inept anywhere in the world (if they even have a functioning government at all), now loudly...... — Donald J. Trump (@realDonaldTrump) July 14, 2019

The president's tweets come amid a dispute between House Speaker Nancy Pelosi and the progressive lawmakers, who have grown impatient with Democratic leadership. The back-and-forth has spilled out into public view over the past two weeks, after Pelosi seemed to minimize the influence of the new members. Ocasio-Cortez then accused Pelosi of "singling out newly elected women of color."

All four of the freshmen congresswomen fired back at the president on Twitter – and the president later fired back at them.

Tlaib was the first to respond Sunday morning, writing: "Want a response to a lawless & complete failure of a President? He is the crisis. His dangerous ideology is the crisis. He needs to be impeached."

Pressley posted a screenshot of the tweets and wrote, "THIS is what racism looks like. WE are what democracy looks like. And we're not going anywhere. Except back to DC to fight for the families you marginalize and vilify everyday." Omar said the president is "stoking white nationalism [because] you are angry that people like us are serving in Congress and fighting against your hate-filled agenda."

Ocasio-Cortez reminded Mr. Trump that she's from the U.S. "You are angry because you can't conceive of an America that includes us. You rely on a frightened America for your plunder," she said.

But you know what’s the rub of it all, Mr. President? On top of not accepting an America that elected us, you cannot accept that we don’t fear you,either. You can’t accept that we will call your bluff & offer a positive vision for this country. And that’s what makes you seethe. — Alexandria Ocasio-Cortez (@AOC) July 14, 2019

Despite her differences with the group, Pelosi rushed to defend them from Mr. Trump's tweets.

"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," Pelosi wrote on Twitter. "I reject @realDonaldTrump's xenophobic comments meant to divide our nation. Rather than attack Members of Congress, he should work with us for humane immigration policy that reflects American values."

I reject @realDonaldTrump’s xenophobic comments meant to divide our nation. Rather than attack Members of Congress, he should work with us for humane immigration policy that reflects American values. Stop the raids - #FamiliesBelongTogether! — Nancy Pelosi (@SpeakerPelosi) July 14, 2019

A handful of 2020 Democratic presidential hopefuls also spoke out against Mr. Trump's comments, including Sen. Elizabeth Warren of Massachusetts.

Hillary Clinton also weighed in with a tweet aimed squarely at the president:

They're from America, and you're right about one thing: Currently their government is a complete and total catastrophe. https://t.co/NvsnFSN8mb — Hillary Clinton (@HillaryClinton) July 14, 2019

On Sunday night, Mr. Trump doubled down. He took to Twitter again to reply to the Democrats who'd spoken out against his earlier missives, saying, "So sad to see the Democrats sticking up for people who speak so badly of our Country and who, in addition, hate Israel with a true and unbridled passion. Whenever confronted, they call their adversaries, including Nancy Pelosi, "RACIST." Their disgusting language...

... ....and the many terrible things they say about the United States must not be allowed to go unchallenged. If the Democrat Party wants to continue to condone such disgraceful behavior, then we look even more forward to seeing you at the ballot box in 2020!"

British Prime Minister Theresa May called President Trump's tweets about the group of mostly American-born Democratic congresswomen "completely unacceptable." The prime minister's spokesman said Monday that in May's opinion, "the language used to refer to these women was completely unacceptable."