Unbowed by mounting national and international criticism of his tweets attacking four Democratic congresswomen, United States President Donald Trump says those complaining about the country can "leave right now".

Key points: Mr Trump told four Democratic representatives to go back to their ancestral countries

Mr Trump told four Democratic representatives to go back to their ancestral countries Three out of the four women are US-born, and all are American citizens

Three out of the four women are US-born, and all are American citizens House Speaker Nancy Pelosi will try to get the House to condemn Mr Trump's remarks

Mr Trump's latest comments came hours after new tweets continued to attack congresswomen Alexandria Ocasio-Cortez, Ilhan Omar, Ayanna Pressley, and Rashida Tlaib — known as "the squad" among the Democrats — labelling them "anti-Semitic" and "anti-American".

He also asked the women to apologise to him, Israel and the United States.

The Democratic 'squad' New York congresswoman Alexandria Ocasio-Cortez is of Puerto Rican descent

New York congresswoman is of Puerto Rican descent Massachusetts congresswoman Ayanna Pressley is of African-American descent

Massachusetts congresswoman is of African-American descent Michigan congresswoman Rashida Tlaib is of Palestinian descent

Michigan congresswoman is of Palestinian descent Minnesota congresswoman Ilhan Omar was born in Somalia and emigrated to the US at age 12 after spending much of her childhood in a Kenyan refugee camp

But in a press conference responding to Mr Trump's new comments, the group turned the heat back on the President, claiming his attacks were a "disruptive distraction" from the policies of his administration.

All four of the women come from racially diverse backgrounds, and only one of them is foreign-born. Mr Trump alluded to the women and asked them to "go back to the places from which they came".

This prompted fierce criticism from the Democrats, who labelled the comments "white nationalist", while other critics said the President was racist.

While Sunday's tweet series did not explicitly mention names — just "Progressive Democrat Women" — his Monday tweets appeared to confirm that he was talking about the squad.

The US Democratic Party ushered in a new generation of congresswomen after mid-term elections in 2018. ( ABC News )

The Democratic representatives that Mr Trump has targeted were elected to Congress in 2018, and have been critical of his administration as well as current Democratic House leaders.

His Monday tweets labelled them "Radical Left Congresswomen", and said that Ms Ocasio-Cortez and her peers hated Israel, the United States and were also "a bunch of Communists".

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The women have drawn the ire of Mr Trump, whom they regularly critique. ( AP: J Scott Applewhite, file photo )

Mr Trump denied to reporters that his initial tweets about the four congressional representatives were racist, and that the accusations do not concern him because "many people" agree with him.

"If you're not happy in the US, if you're complaining all the time, you can leave, you can leave right now," Mr Trump said.

Repeatedly, Mr Trump has painted arriving immigrants as an "infestation", and once conflated white supremacist protesters with anti-racist protesters in response to violence between the groups in Charlottesville, Virginia.

He also launched his political career with false claims that president Barack Obama was not born in the United States.

Congresswomen warn voters 'to not take the bait'

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 2 minutes 5 seconds 2 m 5 s 'Our squad is big' : Congresswomen hit back at Trump tweets

Speaking in public for the first time since the uproar began, the congresswomen used the spotlight to draw attention to the Trump administration policies they've campaigned against, most notably immigration.

"We can not allow these hateful actions by the President to distract us from the critical work to hold this administration accountable to the inhumane conditions at the border that is separating children from their loved ones and caging them up and illegal horrific conditions," Ms Tlaib said.

Ms Pressley labelled Mr Trumps remarks "xenophobic" and "bigoted".

"I encourage the American people … to not take the bait," she said.

Ms Ocasio-Cortez said Mr Trump attacked the congresswomen because he could not defend his own policies.

"He can't look a child in the face and he can't look at all Americans and justify why this country is throwing them in cages," she said.

"So instead he tells us that I should go back to the great borough of the Bronx and make it better. And that's what I'm here to do."

Ms Omar and Ms Tlaib both reiterated their calls for Mr Trump to be impeached.

"This is a President who has said 'grab women by the pussy'. This is a President who's called black athletes 'sons of bitches'. This is a President people who come from black and brown countries 's***holes'," Ms Omar said.

"I've said to people, it is not if he will be impeached but when. So 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."

Prominent Republicans remain silent

Vice-President Mike Pence, left, has not explicitly commented on Mr Trump's remarks. ( Reuters: Win McNamee/Pool )

While Mr Trump claimed that "a lot of people love" his latest Democratic attacks, few prominent Republicans in Congress have had little public reaction to Mr Trump's tweets.

None of the top four Republican leaders in Congress, including Senate Majority Leader Mitch McConnell and House Republican Leader Kevin McCarthy, or their representatives, had any immediate comment.

However, Republican senator Lindsey Graham, a close ally of the President, advised him to "aim higher" during an appearance on cables news channel Fox.

"Don't get personal. Don't take the bait," Mr Graham said.

He said Ms Ocasio-Cortez and her colleagues "are American citizens" who were "duly elected," but agreed with Mr Trump's assessment:

"We all know that AOC and this crowd are a bunch of communists. They hate Israel. They hate our own country," Mr Graham said.

But a few Republicans have pushed back in light of the furore.

Texan congressman Chip Roy said in his own tweet overnight that Mr Trump was "wrong".

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He added that congressional representatives "who refuse to defend America" should not be re-elected next year.

Maine senator Susan Collins, who is up for re-election next year, said Mr Trump's tweet was "way over the line and he should take that down".

Republican senator Patrick Toomey of Pennsylvania said of the Democrats:

"We should defeat their ideas on the merits, not on the basis of their ancestry."

Asked if the President's tweets were racist, Ken Cuccinelli, Mr Trump's acting director of US Citizenship and Immigration Services, told CNN: "I wouldn't go that far, no, certainly not."

US Vice-President Mike Pence's chief of staff, Marc Short, on Monday defended the President's comments in an interview on Fox Business Network, later telling reporters at the White House:

"This is not a universal statement he is making," he said.

ABC/wires