(CNN) President Donald Trump redoubled his racist attacks on a quartet of Democratic congresswomen Monday, insisting they leave the United States if they continue complaining about his policies.

It was an escalation of an attack begun Sunday that prompted House Speaker Nancy Pelosi to announce she would formally introduce a motion to reject the comments. After nearly a day of silence, some Republicans were starting to decry Trump's broadsides, though others -- including members of his administration -- downplayed them.

Trump himself denied his attacks on the four -- all women of color -- were racist . He also said he was unbothered by statements of support from white nationalists, who say they hear common cause in the President's statements.

"It doesn't concern me because many people agree with me," Trump said on the White House South Lawn, where an event focused on American manufacturing took a dark turn toward inflammatory rhetoric as the President defended himself.

On Sunday, the President used racist language to attack progressive Democratic congresswomen, falsely implying they weren't natural-born American citizens.

The group of Democrats -- Reps. Ilhan Omar of Minnesota, Alexandria Ocasio-Cortez of New York, Rashida Tlaib of Michigan and Ayanna Pressley of Massachusetts -- who are women of color and have been outspoken about Trump's immigration policies. Last week, they condemned the conditions of border detention facilities.

Ocasio-Cortez, Tlaib and Pressley are natural-born US citizens, while Omar was born in Somalia and immigrated to the US when she was young. Omar became a citizen in 2000 when she was 17 years old, according to The New York Times

Trump implied in the series of Sunday tweets that the congresswomen weren't born in America and sarcastically suggested, "they go back and help fix the totally broken and crime infested places from which they came."

Asked directly as he walked toward displays of American motorcycles and Air Stream trailers if his tweets were racist , Trump said: "Not at all."

'You can leave'

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Later, Trump declared from behind a podium that if that if the congresswomen don't like the United States, they can leave.

"As far as I'm concerned, if you hate our country, if you're not happy here, you can leave," Trump said in remarks in front of the South Portico.

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

Questioned about Pelosi's assertion that he is attempting to "make America white again," Trump employed a favorite tactic: turning accusations against him around on his accusers.

"That's just a very racist statement," Trump said on the South Lawn.

Originally, Trump did not name who he was attacking in Sunday's tirade. Asked Monday who he's talking about, Trump said: "You can guess."

Those appeared to be references to earlier controversies in which Omar made comments criticizing US support for Israel that were seen as invoking anti-Semitic tropes and stereotypes. A video of her discussing the 9/11 was also seized by conservatives earlier this year as downplaying the terror attacks.

On Monday, Trump also appeared to allude to Ocasio-Cortez, saying she'd cost New York tens of thousands of jobs in her opposition to a New Amazon headquarters in New York. The freshman Democrat was opposed to tax benefits the internet giant would have received.

"As to whether or not they're communists, I would think they might be. But this isn't what our country is about," Trump said. "Nevertheless, they're free to leave if they want. If they want to leave, that's fine. If they want to stay, that's fine. But the people have to know. And politicians can't be afraid to take them on."

It was the President's idea to address his attacks during his "Made in America" event at the White House, a White House official told CNN. Trump told aides he was going to do so before he exited the Oval Office.

Reaction

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Republicans were slow to respond to the President's remarks. But eventually some spoke out against Trump, saying his sentiments were racist and he should apologize.

"I am confident that every Member of Congress is a committed American," Rep. Mike Turner of Ohio tweeted. "@realDonaldTrump's tweets from this weekend were racist and he should apologize. We must work as a country to rise above hate, not enable it."

Other administration officials and GOP lawmakers were less scathing. Speaking at the last-minute White House briefing, Treasury Secretary Steven Mnuchin said he did not believe the President's remarks were racist.

"I think the President clarified his comment. I understand what the President's comment is. I'm not concerned about the President's comment," he said. "That's the last comment I'm going to make on this issue."

Sen. Lindsey Graham of South Carolina, one of the President's top allies in Congress, said during an appearance on Fox News that the Democrats in question were "communists" and "hate Israel." Still, he expressed wariness at Trump's tactics.

"Mr. President, you're right about their policies. You're right about where they will take the country. Just aim higher," he said.

Trump rejected that suggestion during his remarks on Monday.

"I disagree with Lindsey. These are congressmen," he said. "What am I supposed to do, wait for senators?"