Latest updates: Follow our full coverage on the US election
The "uncommitted" movement announced on Thursday it would not be endorsing Vice President Kamala Harris as the Democratic candidate for president.
“Vice President Harris's unwillingness to shift on unconditional weapons policy or to even make a clear campaign statement in support of upholding existing US and international human rights law has made it impossible for us to endorse her,” the group said in a statement.
The anti-war movement garnered about 30 delegates after earning more than 740,000 protest votes in the Democratic primaries, during which voters cast “uncommitted” ballots or left them blank to show support for a ceasefire in Gaza as well as an arms embargo on Israel.
When Ms Harris became the Democratic nominee, after President Joe Biden withdrew from the race in July, uncommitted leaders were initially optimistic that she could shift policy on Gaza. Her campaign also stepped up efforts to reach Arab and Muslim voters.
The lack of an endorsement from the uncommitted movement and potential loss of the Arab and Muslim-American vote may present a challenge for the Harris campaign as it tries to clinch swing states such as Michigan and Pennsylvania.
As the war approaches its first anniversary, more than 41,200 Palestinians have been killed, according to local authorities, and much of Gaza reduced to rubble. The war began after Hamas militants infiltrated southern Israel and killed about 1,200 people, according to Israeli tallies, taking another 250 hostage.
Layla Elabed, co-director of the uncommitted movement, said it not only comprises Arab and Muslim Americans, but has grown to include labour unions, progressive groups and climate change activists.
"We need a policy shift and we need promises around a policy shift from Vice President Harris in order to be able to mobilise uncommitted voters in key swing states like Michigan to vote for her in November," Ms Elabed told The National.
"But despite all of that work, and despite the fact that we actually have an infrastructure to turn out votes, it's fallen on deaf ears."
Imposing an arms embargo on Israel is a central demand of the uncommitted movement as well as Arab-American groups and allies, who argue there is ample evidence that Israel is deliberately attacking Palestinian civilians and infrastructure in Gaza.
Ms Elabed said that the group had been told by officials that Ms Harris had moved on the Gaza issue as much as she could.
While some say Ms Harris has made it a point during her campaign to recognise Palestinian suffering, the Vice President has at times shut down anti-war protesters during campaign events and has continued to push the same Biden administration messaging, which has not moved the needle on Gaza ceasefire efforts.
The tension with the Harris campaign was on full display during the Democratic National Convention in Chicago last month, when organisers refused the uncommitted movement's request to allow a Palestinian-American speaker on stage. Meanwhile, the parents of an Israeli-American hostage received a prime-time speaking slot.
Uncommitted delegates who were attending the DNC held a sit-in outside the main convention hall in protest. The leaders of the movement requested that Ms Harris meet delegates by September 15. She did not.
Ms Elabed said that while the group will not endorse Ms Harris, it continues to oppose Donald Trump, the former president and Republican nominee. It will also not recommend voting for a third-party candidate, which could give the advantage to Mr Trump.
Many Arab-American voters support Green Party candidate Jill Stein due to her pro-Palestinian stance, a poll carried out by the Arab-American Anti-Discrimination Committee found in July.
The movement, Ms Elabed said, would continue to mobilise voters to head to the polls, as there are other important issues as well as progressive candidates on the ballot. She also said efforts would be made to continue to call on Ms Harris to adopt a different policy on Gaza.
"It was a difficult decision," Ms Elabed said, "because obviously, our movement is also committed to blocking Trump."
The statement from the movement said members would continue efforts to push “for life-saving policy change which ends the bombing of Gaza and ends US support for the Israeli military's war crimes”.
Patrick deHahn contributed to this report from New York
