Representative Rashida Tlaib, an outspoken voice for a cease-fire in the Israel-Hamas war, released a video on Friday that accused President Joe Biden of supporting the genocide of Palestinians.

“Mr President, the American people are not with you on this one,” Tlaib says in the video. “We will remember in 2024.”

After she speaks, the screen goes dark and a message appears in white lettering stating: “Joe Biden supported the genocide of the Palestinian people. The American people won’t forget. Biden, support a cease-fire now. Or don’t count on us in 2024.”

Tlaib, the only Palestinian American in Congress, has been on the leading edge of a group of progressive lawmakers criticising Biden’s embrace of Israel since the attack by Hamas on October 7, saying his actions have helped enable the deaths of Palestinian civilians in Israel’s response. She beat back an attempt to censure her in the House this week over her comments on the war and is facing attack ads from a Democratic pro-Israel group.

But accusing Biden of supporting genocide marks an extraordinary broadside against the president by a lawmaker from his own party. The language in the video also threatens to widen a tense fissure within the Democratic Party on the conflict, with pro-Palestinian and pro-Israeli members of the party trading accusations of bigotry.

Biden faces enormous pressure from those crosscurrents in the party as he has sought to stand with Israel — the US’s closest ally in West Asia, which last month saw the deadliest day for Jews since the Holocaust — and to help ease the suffering of Palestinian civilians as Israel pummels the Gaza Strip with airstrikes and a ground invasion.