WASHINGTON — US President Donald Trump came under fire from Democrats and even some members of his own Republican Party on Monday after launching an extraordinary xenophobic attack on four progressive Democratic congresswomen.

"All they do is complain," Trump told reporters at a White House event featuring products "Made in America".

"These are people that hate our country," he said of the four Democratic lawmakers.

"If you're not happy here, you can leave."

Trump also accused the four first-term Democratic congresswomen - who are of Hispanic, Arab, Somali and African-American origin - of having "love" for US "enemies like Al-Qaeda".

Asked by a reporter whether he was concerned that many people saw his comments as racist, Trump said: "It doesn't concern me because many people agree with me."

Several hours after his remarks, the four - Alexandria Ocasio-Cortez of New York, who is of Puerto Rico origin, Ilhan Omar of Minnesota, who is of Somali origin, Rashida Tlaib of Michigan, the first Palestinian-American woman elected to Congress, and Ayanna Pressley of Massachusetts, who is African-American - hit back at a news conference.

Pressley condemned Trump's "xenophobic and bigoted" comments and said "we will not be silenced".

Omar said Trump made a "blatantly racist attack" on four lawmakers "of color".

"This is the agenda of white nationalists," she said.

Omar and Tlaib repeated calls for Trump to be impeached.

'Destructive'

The president first attacked the lawmakers with a series of tweets on Sunday, saying they should "go back" to their countries of origin if they didn't like the United States.

His comments prompted outrage from Democrats - and, initially, silence from Republicans.

On Monday, several of his party faithful began to speak up.

"My view is that what was said and what was tweeted was destructive, was demeaning, was disunifying, and frankly it was very wrong," said Senator Mitt Romney, a Republican from Utah.

"There is no excuse for the president's spiteful comments - they were absolutely unacceptable and this needs to stop," said Senator Lisa Murkowski, a Republican from Alaska.

"We must demand a higher standard of decorum and decency."

Republican Senator Susan Collins of Maine said she disagreed with the policies espoused by the "far-left" Democratic lawmakers but Trump was "way over the line".

For Republican Senator Pat Toomey of Pennsylvania, "the citizenship of all four is as valid as mine".

"They are entitled to their opinions, however misguided they may be," he said.

Texan Will Hurd, the only black Republican in the House of Representatives, told CNN that Trump's behavior was "unbecoming of the leader of the free world".

And Senator Tim Scott, a black Republican from South Carolina, criticized the president for using "unacceptable personal attacks and racially offensive language".

'Cold, hard strategy'

Trump's comments appear to be aimed at galvanizing his mostly white electoral base ahead of the 2020 presidential vote - while also stoking racial tensions and divisions among his political opponents.

"With his deliberate, racist outburst, @realDonaldTrump wants to raise the profile of his targets, drive Dems to defend them and make them emblematic of the entire party," said David Axelrod, who served as chief strategist for Barack Obama's two White House campaigns.

"It's a cold, hard strategy," Axelrod said on Twitter.

"Fasten your seatbelts, it will only get worse as the election approaches."

"The voters will decide," Trump told reporters.

"If (the Democrats) want to gear their wagons around these four people, I think they're going to have a very tough election, because I don't think the people of the United States will stand for it."

In his initial Twitter attack on Sunday, Trump - who before becoming president pushed the racist "birther" conspiracy theory that Obama was not born on US soil -said the congresswomen came from corrupt, poorly managed countries to which they should return.

Ocasio-Cortez, Tlaib and Pressley were all born in the United States while Omar arrived from war-torn Somalia when she was a child.

Former vice president Joe Biden, who is seeking the 2020 Democratic presidential nomination, denounced Trump as the most "openly racist and divisive" president in US history.

"Go home to your country? It's sickening, it's embarrassing," Biden said.

Nancy Pelosi, the Democratic speaker of the House of Representatives, has had a tenuous relationship with the four left-leaning congresswomen but she jumped to their defense.

"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 said.

Pelosi said she was seeking Republicans to co-sponsor a House resolution "condemning the president's xenophobic tweets" and "characterization of immigrants".

Democratic Senator Chuck Schumer of New York said he planned to do the same in the Senate. — AFP