President Trump on Monday stepped up his attacks on four progressive, minority Democratic lawmakers, which were widely condemned by Democrats - and some Republicans - as racist and unbecoming of an American president.

One day after Trump said the four women should "go back" to their home countries, even though all are U.S. citizens, the president denied he was being racist and expressed no remorse when told that white nationalist groups found common cause with his message.

"It doesn't concern me because many people agree with me," Trump told reporters on the South Lawn of the White House during an event highlighting American manufacturing.

Trump said the lawmakers "hate our country," harbor hatred of Jews and love for terrorist groups and are "free to leave" the U.S. if they choose.

"They can leave. And you know what? I'm sure there will be many people that won't miss them. But they have to love our country. They're congresspeople," he said.

The president's attacks were aimed at Democratic Reps. Alexandria Ocasio-Cortez (N.Y.), Rashida Tlaib (Mich.), Ayanna Pressley (Mass.) and Ilhan Omar (Minn.) The first three were all born in the U.S. Omar is a naturalized citizen who was a refugee from Somalia.

"I'm saying that they're socialists definitely. As to whether or not they're communists, I would think they might be," Trump said, adding in an apparent shot at his critics that "politicians can't be afraid to take them on."

During a press conference Monday, Omar accused Trump of launching a "blatantly racist attack" against her and her three colleagues.

"This is the agenda of white nationalists. Whether it is happening in chat rooms, or it's happening on national TV and now, it's reached the White House garden," she said.

"We don't leave the things that we love, and when we love this country, what that means is that we propose the solutions to fix it," said Ocasio-Cortez, who also spoke at the news conference.

The president's sustained barrage appeared to be designed to fire up his mostly white political base ahead of the 2020 presidential election. But it also galvanized infighting-plagued Democrats in the House and exposed rifts within the Republican Party over Trump's heated rhetoric.

Trump spoke shortly after Speaker Nancy Pelosi (D-Calif.) rallied support for a forthcoming resolution that she said would condemn the president's statements as xenophobic. That move followed Trump doubling down on his criticism of the lawmakers in a string of Monday morning tweets, in which he called on them to apologize for their "foul language & racist hatred."

The president responded by accusing Pelosi of making "a very racist statement" when she said he wanted to "make America white again."

"If they 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 are going to stand for it," Trump said of the Democrats.

Though they initially remained silent after Trump's attacks, a growing number of GOP lawmakers who mostly represent swing states and congressional districts criticized the president's comments on Monday.

"I am confident that every Member of Congress is a committed American. @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," tweeted Rep. Mike Turner (Ohio), a Republican who represents a district considered safe by the nonpartisan Cook Political Report.

Rep. Will Hurd (Texas), the lone black House Republican, who represents a competitive district along the southern border, told CNN that Trump's tweets were "racist and xenophobic."

The Senate's only black GOP member, Tim Scott (S.C.), struck a similar tone when he referred to Trump's tweets as "racially offensive." He also said the president took the focus off the Democrats' own internal squabbles on race.

"Prior to this weekend, we saw the Democratic Party embroiled in racial controversy," Scott said in a statement, citing the battle between 2020 presidential candidates Sen. Kamala Harris (D-Calif.) and former Vice President Joe Biden over busing.

The internal Democratic divisions were widened by a public feud between Pelosi and the four progressive lawmakers.

"Instead of sharing how the Democratic Party's far-left, pro-socialist policies - not to mention the hateful language some of their members have used against towards law enforcement and Jews - are wrong for the future of our nation, the president interjected with unacceptable personal attacks and racially offensive language," Scott said.

But Trump was unbowed by such criticism. He spent the bulk of his time on Monday singling out Omar, a frequent target of the president's criticism.

He said Omar, who along with Tlaib is one of the first Muslim women to be elected to Congress, "hates Jews."

Trump made similar comments earlier this year after Omar was accused of using anti-Semitic tropes when criticizing Israel and its supporters.

He also appeared to reference a six-year-old interview, in which Omar joked about the tone a former professor used to talk about al Qaeda, which resurfaced in an April Fox News report.

In a bizarre aside, Trump went after Ocasio-Cortez for helping to block Amazon from building a second headquarters in New York City. Trump has long been a vocal critic of the online retail giant.

The president was prepared to defend his tweets, even though he initially cut off reporters who asked about them because "this is really about economic development."

He carried typed, bullet-pointed notes onto the South Lawn with suggestions in the margins written in his preferred black Sharpie. Omar's name was spelled "Ohmar" and al Qaeda was spelled "Alcaida," according to a photo taken by a Washington Post photographer.

Trump's attacks on the progressive lawmakers came as his administration sought to block Central American migrants from claiming asylum and carried out raids aimed at deporting immigrants living in the U.S. illegally, hard-line moves that will likely please his base that sees immigration as a central issue.

All four Democratic women have vocally criticized Trump over the conditions inside migrant detention centers, with Ocasio-Cortez likening them to "concentration camps."

Several of Trump's aides and allies came to his defense amid the onslaught of criticism of the president's Sunday remarks.

"I don't find them racist," Treasury Secretary Steven Mnuchin told reporters during a Monday briefing at the White House. "The president just went on and clarified his comments. I think he speaks for himself on that, and he was very clear."

"President Trump loves this country & doesn't like it when elected officials constantly disparage it & spew anti-Semitic rhetoric," tweeted Trump campaign communications director Tim Murtaugh. "All Dems have leapt to defend the 'Blame America First' crowd when they really should be defending America & rooting out anti-Semitism in their ranks."

Trump ignited the controversy on Sunday, when he accused the four Democratic women "who originally came from countries whose governments are a complete and total catastrophe" of "viciously telling the people of the United States how our government is to be run."

"Why don't they go back and help fix the totally broken and crime infested places from which they came," he tweeted.

Brett Samuels contributed. Updated at 6:26 p.m.