U.S. President Donald Trump upped his attack on four Democratic congresswomen on Tuesday morning on Twitter, calling them "pro-terrorist."

Trump wrote, "The Democrat Congresswomen have been spewing some of the most vile, hateful, and disgusting things ever said by a politician in the House or Senate, & yet they get a free pass and a big embrace from the Democrat Party. Horrible anti-Israel, anti-USA, pro-terrorist & public.....

.....shouting of the F...word, among many other terrible things, and the petrified Dems run for the hills. Why isn’t the House voting to rebuke the filthy and hate laced things they have said? Because they are the Radical Left, and the Democrats are afraid to take them on. Sad!"

Defiant in the face of widespread censure, Trump escalated his demand for four Democratic congresswomen of color to leave the U.S. “right now,” stoking the discord that helped send him to the White House and claiming “many people agree with me.”

At the Capitol, the four lawmakers fired back, condemning what they called “xenophobic bigoted remarks” and renewing calls for Democrats to begin impeachment proceedings.

Trump had called on the four to “go back” to their “broken and crime-infested” countries in tweets that have been widely denounced as racist. His remarks were directed at Reps. Ilhan Omar of Minnesota, Alexandria Ocasio-Cortez of New York, Ayanna Pressley of Massachusetts and Rashida Tlaib of Michigan. All are American citizens, and three of the four were born in the U.S.

Trump on Monday falsely claimed Omar had praised the terrorist group Al-Qaeda. Trump tweeted "when I hear people speaking about how wonderful Al-Qaeda is."

He later doubled down "That was Omar. How great Al-Qaeda is." And he said, "She said you can hold their chest out, you can -- 'When I think of America, huh. When I think of al Qaeda, I can hold my chest out.'"

CNN fact checked the claim, noting "Omar has not praised Al-Qaeda or said she can hold her "chest out" when thinking of Al-Qaeda. Trump was inaccurately describing remarks she made in 2013 about how one of her college professors acted when he discussed Al-Qaeda."

Associated Press contributed to this report.