House Speaker Nancy Pelosi announced on Sunday that she has taken steps to ensure the safety of Rep. Ilhan Omar following President Donald Trump's retweet of a video that purports to show the Minnesota Democrat being dismissive of the September 11 terrorist attacks.

The California Democrat also called on Trump to take down the video. Soon after her public request, the video was no longer pinned to the top of Trump's twitter feed.

Pelosi was among Democrats who had criticised Trump over the tweet, with some accusing him of trying to incite violence against the Muslim lawmaker who has already seen one upstate New York man face criminal charges for making death threats against her.

The White House defended Trump earlier on Sunday, saying the president has a duty to highlight Omar's history of making comments that others find offensive and that he wished no “ill will” upon the first-term lawmaker.

Pelosi, who was traveling in London, issued a statement saying she had spoken with congressional authorities after Trump's tweet “to ensure that Capitol Police are conducting a security assessment to safeguard Congresswoman Omar, her family and her staff.”

“They will continue to monitor and address the threats she faces,” the speaker said. She called on Trump to discourage such behaviour.

“The President's words weigh a ton, and his hateful and inflammatory rhetoric creates real danger,” Pelosi said. “President Trump must take down his disrespectful and dangerous video.”

The video in Trump's tweet included a snippet from a recent speech Omar gave to the Council on American-Islamic Relations, in which she described the 2001 terrorist attack on the World Trade Centre as “some people did something,” along with news footage of the hijacked airplanes hitting the Twin Towers.

Trump captioned his tweet with: “WE WILL NEVER FORGET!”

Critics accuse Omar of offering a flippant description of the assailants behind the attack that killed nearly 3,000 people. She later sought to defend herself by tweeting a quote from President George W. Bush.

Days after 9/11, the Republican president referred to the attackers as “people.”

Neither Trump's tweet nor the video included 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 atop Trump's Twitter feed for much of Sunday, with more than 9 million views. It remained lower in the feed after Pelosi made her request for the video to be pulled.

Sanders questioned why Democrats weren't following Trump's example and calling out Omar, too. Democrats who criticised the president over the tweet defended Omar. Some also noted 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,” 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.”

Omar repeatedly has 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 lawmakers support Israel for pay and said she isn't criticising Jews. But she refused to take back a tweet in which she suggested American supporters of Israel “pledge allegiance” to a foreign country.

Rep. Jerry Nadler, a New York Democrat whose constituents include Manhattan's financial district, which was targeted on September 11, 2001, said he had no issues with 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.

Sanders commented on “Fox News Sunday” and ABC's “This Week.” Nadler appeared on CNN's “State of the Union.