Ms Omar, the first Somali-American elected to Congress, has been forced to defend herself in recent days following an event last week in which she claimed she was being pressured to pledge “allegiance” to Israel.
“I want to talk about the political influence in this country that says it is OK for people to push for allegiance to a foreign country,” she told an audience in Washington on Wednesday.
She doubled down on her comments on Sunday, tweeting that she should not have to “have allegiance/pledge support to a foreign country” in order to serve in Congress.
Late on Monday evening, Mr Trump tweeted: “Representative Ilhan Omar is again under fire for her terrible comments concerning Israel. Jewish groups have just sent a petition to Speaker Pelosi asking her to remove Omar from Foreign Relations Committee. A dark day for Israel!”
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Ms Omar’s comments were also criticised by members on both sides of the congressional aisle, with some claiming the suggestion of “allegiance” to Israel invokes antisemitic tropes.â€¨
"Throughout history, Jews have been accused of dual loyalty, leading to discrimination and violence, which is why these accusations are so hurtful,” tweeted Nita Lowey, a fellow Democratic congresswoman.
But Ms Omar received support from Alexandria Ocasio-Cortez, who said the criticism of Ms Omar was "hurtful" and that “discussion and debate on this issue is fair and merited”.
"One of the things that is hurtful about the extent to which reprimand is sought of Ilhan is that no one seeks this level of reprimand when members make statements about Latinx + other communities (during the shutdown, a GOP member yelled 'Go back to Puerto Rico!' on the floor)," Ms Ocasio-Cortez tweeted on Tuesday.
“I remember a time when it was ‘unacceptable’ to question the Iraq War,” she also tweeted on Monday evening. “All of Congress was wrong, including both GOP & Dem Party, and led my generation into a disastrous + wrong war that virtually all would come to regret.”
Ilhan Omar: Democratic congresswoman interrogates Donald Trump's Venezuela envoy Elliot Abrams
Israeli journalist Mairav Zonszein was among those who implied Ms Ilhan's criticism of Israel and US foreign policy was being wrongly conflated with antisemitism.
Responding to Mr Trump’s tweet, she said: “Another admission it’s about criticising Israel and US foreign policy. Nothing to do with Jews.
"This is why I can’t believe the American Jews doubling down on Ilhan Omar. Do they really not see the real danger?"