Democratic congresswoman Ilhan Omar has said she has faced increased death threats since US President Donald Trump retweeted a video that purports to show her being dismissive of the 2001 terrorist attacks.
“This is endangering lives,” she said, accusing Mr Trump of fomenting right-wing extremism.
Ms Omar said she had experienced “an increase in direct threats on my life”, adding: “It has to stop.”
Her statement followed an announcement by House Speaker Nancy Pelosi that she has taken steps to ensure the safety of the Minnesota Representative and calling for Mr Trump to take down the video.
Soon after Ms Pelosi’s statement, the video disappeared as a pinned tweet at the top of Mr Trump’s Twitter feed, but it was not deleted.
Ms Pelosi was among Democrats who had criticised Mr Trump over the tweet, with some accusing him of trying to incite violence against the Muslim politician.
An upstate New York man was recently charged with making death threats against her.
White House press secretary Sarah Sanders defended Mr Trump, saying the president has a duty to highlight Ms Omar’s history of making comments that others deem anti-Semitic or otherwise offensive and that he wished no “ill will” upon the first-term politician.
But Ms Omar said that since Mr Trump retweeted the video on Friday night, she has received many threats on her life that referred or replied to the posted video.
“Violent crimes and other acts of hate by right-wing extremists and white nationalists are on the rise in this country and around the world,” she said.
“We can no longer ignore that they are being encouraged by the occupant of the highest office in the land.”
She said: “We are all Americans.”
Earlier, Ms Pelosi issued a statement while travelling in London saying she had spoken with congressional authorities “to ensure that Capitol Police are conducting a security assessment to safeguard Congresswoman Omar, her family and her staff”.
Ms Pelosi said officials will continue to monitor and assess threats against Ms Omar, and called on Mr Trump to discourage such behaviour.
“The president’s words weigh a ton, and his hateful and inflammatory rhetoric creates real danger,” Ms Pelosi said.
“President Trump must take down his disrespectful and dangerous video.”
The video in Mr Trump’s tweet included a snippet from a recent speech Ms Omar gave to the Council on American-Islamic Relations, in which she described the September 11 2001 terrorist attack on the World Trade Centre as “some people did something”, along with news footage of the hijacked planes hitting the Twin Towers.
Mr Trump captioned his tweet with: “WE WILL NEVER FORGET!”
Critics accuse Ms Omar of being flippant in describing the perpetrators of the attacks that killed nearly 3,000 people.
She later sought to defend herself by tweeting a quote from George W Bush, in which the Republican president referred to the attackers as “people” just days after 9/11.
Neither Mr Trump’s tweet nor the video included Ms Omar’s full quote or the context of her comments, which were about Muslims feeling that their civil liberties had eroded after the attacks.
The tweet was posted at the top of Mr Trump’s Twitter feed for much of Sunday, with more than nine million views.
It remained lower in the feed after Ms Pelosi requested that the video be pulled.
Ms Sanders questioned why Democrats were not following Mr Trump’s example and calling out Ms Omar.
Democrats who criticised the president over the tweet defended Ms Omar, with some noting their past disagreements with her.
“Certainly the president is wishing no ill will and certainly not violence towards anyone, but the president is absolutely and should be calling out the congresswoman for her – not only one time – but history of anti-Semitic comments,” Ms Sanders said.
“The bigger question is why aren’t Democrats doing the same thing? It’s absolutely abhorrent the comments that she continues to make and has made and they look the other way.”
Ms Omar has repeatedly pushed fellow Democrats into uncomfortable territory with comments about Israel and the strength of the Jewish state’s influence in Washington.
She apologised for suggesting that politicians support Israel for pay and said she is not criticising Jews.
But she refused to take back a tweet in which she suggested American supporters of Israel “pledge allegiance” to a foreign country.
Representative Jerry Nadler, a New York Democrat who represents Manhattan’s financial district, which was targeted on 9/11, said he had no issues with Ms Omar’s characterisation of the attack.
“I have had some problems with some of her other remarks, but not – but not with that one,” he said.