"All they do is complain," Trump told reporters at a "Made in America" event at White House. (Reuters)

President Donald Trump stepped up his attacks on four progressive Democratic congresswomen on Monday, saying if they're not happy in the United States "they can leave."

"All they do is complain," Trump told reporters at a "Made in America" event at the White House. "These are people that hate our country. They hate it, I think, with a passion.

"If you're not happy here, you can leave," he added. "So all I'm saying is if they want to leave, they can leave."

Trump also accused the four Democratic congresswomen, all of whom are women of color, of having "love" for US "enemies like Al-Qaeda."