A Muslim American congresswoman's remarks deemed anti-Semitic by some colleagues has exposed deep fault lines among Democrats, with the party seeking to contain the damage with passage Thursday of a measure condemning bigotry and hate.

After days of soul-searching and febrile recrimination, the Democratic leadership appeared desperate to move past a controversy that has left the party split two months since reclaiming the House majority.

House Speaker Nancy Pelosi unveiled a resolution that she called the "strongest possible opposition" to anti-Semitism, Islamophobia, and white supremacist bigotry.

The decision followed acrimonious debate over how to reprimand Minnesota Democrat Ilhan Omar, who sparked a firestorm over repeated criticisms of Israel and a powerful pro-Israel lobby in Washington that exerts influence in US politics.

The resolution passed overwhelmingly, 407 to 23, with all Democrats voting in favor including Omar herself.

The former Somali refugee had been assailed for suggesting supporters of Israel are urging lawmakers to have "allegiance to a foreign country."

Lawmakers expressed outrage, warning that Omar was peddling in age-old anti-Semitic tropes about Jews having dual loyalties.

Weeks earlier she drew ire for suggesting Jewish political power comes through their money, and that the American Israel Public Affairs Committee lobbying group was paying US politicians to support Israel.

A vote had been expected on a resolution specifically condemning anti-Semitism.

The resolution does not mention Omar by name, and some Republicans complained that the measure's original intent was "watered down."

Omar joined the two other Muslims in Congress, Rashida Tlaib and Andre Carson, in praising the measure's passage.

"It's the first time we have voted on a resolution condemning Anti-Muslim bigotry in our nation's history," they said, noting the worrying rise of extremism in America.

"Our nation is having a difficult conversation and we believe this is great progress."

Some Democrats including three 2020 presidential contenders Bernie Sanders, Elizabeth Warren and Kamala Harris, expressed frustration that Omar faced an implicit rebuke, while racist statements by Trump and other Republicans go largely unchallenged.

"We must not... equate anti-Semitism with legitimate criticism of the right-wing Netanyahu government in Israel," said Sanders, who is Jewish.