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

“Mr. President, the American people are not with you on this one,” Ms. 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.”

Ms. Tlaib, the only Palestinian American in Congress, has been on the leading edge of a group of progressive lawmakers criticizing Mr. Biden’s embrace of Israel since the attack by Hamas on Oct. 7, saying his actions have helped enable the deaths of Palestinian civilians in Israel’s response. She already 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 Mr. 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 an already tense fissure within the Democratic Party on the conflict, with pro-Palestinian and pro-Israeli members of the party trading accusations of bigotry.

A White House spokesman declined to comment on the video.

Mr. Biden faces enormous pressure from those crosscurrents in the party as he has sought to stand with Israel — the United States’ closest ally in the Middle East, 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.

The Biden administration has called for “humanitarian pauses” to allow aid to get to civilians and for more people to leave the Gaza Strip. Prime Minister Benjamin Netanyahu seems to have rejected that plea, saying any end to Israel’s military campaign would be contingent on the release of over 200 hostages Hamas abducted in the Oct. 7 attack.

Mr. Biden has also grown more critical of the Israeli government’s response as the death toll in Gaza has ballooned and the humanitarian crisis has deepened, even while declaring unambiguous support for Israel and its right to defend itself.

The video posted by Ms. Tlaib opens with a clip of Mr. Biden stating that the United States stands with Israel, before cutting to videos of Israeli airstrikes in the Gaza Strip, children bleeding in medical tents, bodies lying in rubble and protests around the United States calling for a cease-fire.

One clip features a demonstration in Michigan in which protesters chanted “from the river to the sea” — a chant used by Hamas that many Jews view as calling for the eradication of Israel.

In a follow-up post on X, formerly Twitter, Ms. Tlaib wrote, “From the river to the sea is an aspirational call for freedom, human rights, and peaceful coexistence, not death, destruction, or hate.”

The video contained just the latest in a series of statements that have put Ms. Tlaib at odds with many in her party.

“As the Israeli government carries out ethnic cleansing in Gaza, President Biden is cheering on Netanyahu, whose own citizens are protesting his refusal to support a cease-fire,” Ms. Tlaib said on Thursday. “We must be laser focused on saving lives, no matter their faith or ethnicity.”

The House struck down a resolution on Thursday to formally rebuke Ms. Tlaib, with about two dozen Republicans joining Democrats in opposition. The resolution, which was brought by Representative Marjorie Taylor Greene, Republican of Georgia, accused Ms. Tlaib of “antisemitic activity” and referred to an Oct. 18 protest in a House office building, in which Ms. Tlaib accused Israel of genocide, as an “insurrection.”

Around 20 far-left members of the House have signed onto a resolution urging the White House to call for a cease-fire and de-escalation of violence in the Middle East. Senator Richard J. Durbin of Illinois, the No. 2 Democrat in the Senate, on Thursday became the first senator to call for a cease-fire if the hostages are released, and Pope Francis called for an end to the war on Sunday.