Jewish organizations in the United States are planning a demonstration for Tuesday on the National Mall in Washington, with tens of thousands expected to gather in a show of solidarity with Israel as it wages war in Gaza in response to the Oct. 7 attack by Hamas.

The rally, called the March for Israel, comes after large protests across the United States and in world capitals denouncing the Israeli military campaign in Gaza, which has been plunged into a humanitarian crisis.

The event is intended by organizers in part as a response to critics of Israel, where about 1,200 people were killed in the Hamas attack.

“Over the last week and a half,” said Eric Fingerhut, president of the Jewish Federations of North America, which is helping organize the march, “it became clear that even though every poll, every data point shows that the American people overwhelmingly support Israel in its battle against Hamas, we were increasingly hearing from opposing voices who are on the fringe but who are very loud.”

The march was quickly arranged, and Jewish federations around the country, as well as schools, synagogues and community centers, are sending buses of attendees.

Educators, artists, students and relatives of some of the hundreds of hostages seized by Hamas are scheduled to appear, along with the president of Israel, Isaac Herzog, and a host of U.S. lawmakers, including Speaker Mike Johnson, Republican of Louisiana, and the Senate majority leader, Chuck Schumer, Democrat of New York.

Most U.S. lawmakers have rejected calls for a cease-fire. They maintain that Israel’s military campaign — which the Health Ministry in the Hamas-run Gaza Strip says has killed more than 10,000 people — is justified by the imperative to eradicate Hamas.

While U.S. policy has been staunchly pro-Israel so far, there has been growing pushback in congressional offices and the Biden administration, as well as among Democratic voters generally, over how the war has been unfolding, and its toll on noncombatants, especially children.

Mr. Fingerhut said the march was intended in part to remind the politicians in Washington that “the majority of the American people” support Israel’s actions, even if they disagree on other issues. Jewish groups that have at times clashed over the right approach to the Israeli-Palestinian conflict have announced plans to attend the march.

Mr. Fingerhut said the march was also intended to show unity in the face of reports of rising numbers of antisemitic incidents around the country in recent weeks, which he called “an attempt to intimidate the Jewish community and others who support Israel.”