A man has pleaded guilty to threatening to kill Ilhan Omar - one of four Democratic congresswomen known as The Squad.
Patrick Carlineo, 55, called the Minnesota representative's office in March, telling a staffer that the congresswoman was a "terrorist" and that he would "put a bullet in her f****** skull," according to prosecutors.
Ms Omar, a Somali-American, is among the first Muslim women in Congress. Her office had no immediate comment on Carlineo's plea.
She is one of four congresswomen - including Rashida Tlaib, Alexandria Ocasio-Cortez, and Ayanna Pressley - who spoke out after Donald Trump attacked the group on Twitter.
According to a criminal complaint, Carlineo later told the FBI that he is a patriot, hates people he perceives to be radical Muslims in the US government, and loves the Republican president.
US Attorney James Kennedy Jr. said the case highlights that free speech rights carry the responsibility "that individuals not make threats to harm lawmakers simply because they may disagree with them."
Carlineo's lawyer, Sonya Zoghlin, says Carlineo is passionate about his political beliefs and his right to express them.
"He has taken responsibility for using threatening and inappropriate language to express those beliefs in this instance," she said in an email, adding that Carlineo never intended to harm Ms Omar and never made any plans to do so.
Carlineo's plea included admitting he illegally had guns. He'd been barred from possessing them after a 1998 felony criminal mischief conviction, prosecutors said. His sentencing is set for February
Ms Omar has faced criticism from Mr Trump, who suggested she was married to her brother, while others slammed remarks she made in recent months about Israel, Jewish influence in Washington, and 9/11.
She has apologised for suggesting that politicians support Israel for money, has said she was not criticising Jews, and has said that criticising the Israeli government is not anti-Semitic.
Last month, a North Dakota state senator said he was sorry for posting a long-debunked photo that purported to show Omar holding a weapon at an Al-qaeda training camp.
But Republican Oley Larsen, added that he wouldn't apologise to Ms Omar.