Before Vice President Kamala Harris confronted pro-Palestinian and anti-Gaza-war protesters on Wednesday at a campaign rally in Detroit, she faced demands from the leaders of a group that has mobilized voters to protest the U.S. government’s support for Israel.

The founders of the Uncommitted National Movement, the group that mobilized more than 100,000 people to withhold their votes from President Biden in this year’s Michigan primary over his support for Israel’s war against Hamas in Gaza, were among those invited to welcome Ms. Harris and her new running mate, Gov. Tim Walz of Minnesota, to Michigan in a photo line.

There, the founders, Abbas Alawieh and Layla Elabed, said they asked Ms. Harris for a meeting to discuss an arms embargo on Israel. After 10 months of war, Gazan health officials say nearly 40,000 people, many of them women and children, have been killed.

In a statement, a Harris campaign spokesman said only that “in this brief engagement,” the vice president “reaffirmed that her campaign will continue to engage with those communities.”

Ms. Harris has emerged as a more empathetic voice in the administration, elevating the plight of innocent Palestinians who have been killed, starved and displaced in Israel’s war against Hamas. And while she has reiterated the United States’ support for Israel’s right to defend itself, she has issued the most forceful condemnation of some of Israel’s tactics. But crucial Democratic voting blocs who oppose the war — including Arab Americans in battleground states — have demanded more action, particularly for the United States to stop supplying Israel with weapons that have been used to kill scores of civilians.

In addition to an arms embargo on Israel, the Uncommitted leaders have asked for convention speaking roles for a representative of their group and a Palestinian pediatrician.