WASHINGTON, Aug. 12 — Thousands of people rallied near the White House on Saturday to protest what they described as Israeli aggression in Lebanon and the United States’ unwavering support for Israel.

The diverse crowd included many Arab-Americans and Muslims, college students and families, as well as veterans of prior demonstrations against the war in Iraq.

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“We want to know why our tax money is going to support war crimes,’’ said Mounzer Sleiman, vice chairman of the National Council of Arab-Americans, one of more than 15 speakers who addressed the protesters gathered in Lafayette Park, across from the White House, under a cloudless sky.

The crowd erupted periodically in chants, “Israel out of Lebanon now” and “Free, free Palestine.’’

Dr. Khalil A. Katato of West Bloomfield, Mich., an oncologist who came to Washington by bus with his wife and five children, said, “We are protesting U.S. support of Israeli aggression on the Palestinian and Lebanese people.’’

His wife, Daad Katato, said she made the trip to protest the war in Iraq, and to show sympathy for children killed or injured during Israel’s military operations in Lebanon and the Gaza Strip.

The criticism of Israel at Saturday’s rally contrasted with the sentiment in Congress, where support for Israel is overwhelming and bipartisan. By a vote of 410 to 8, the House last month expressed “strong support’’ for Israel and condemned Hezbollah and Hamas for armed attacks on Israeli territory. The Senate approved a similar resolution by voice vote.

President Bush was at his ranch in Crawford, Tex., winding up a 10-day vacation. He was due back at the White House on Sunday.

At the rally on Saturday, the prevailing sentiments were expressed in signs held aloft by marchers: “Occupation is a crime — Iraq, Lebanon, Palestine.” “Stop Israeli terrorism.” “No justice, no peace.’’

Brian Becker, national coordinator of a coalition called Act Now to Stop War and End Racism, a sponsor of the rally, asserted that President Bush had given Israel a green light to crush Hezbollah in Lebanon, then “sent cluster bombs to the Israeli Defense Forces to kill Lebanese children.’’ Israel has asked the Bush administration to speed delivery of rockets armed with cluster munitions, which could be used to strike Hezbollah missile sites in Lebanon, and a senior American official said this week that the request was likely to be approved.

Several speakers at the rally criticized Mr. Bush for mentioning the religious background of those arrested this week in a plot to blow up airplanes flying from Britain to the United States. Mr. Bush said the plot showed that “this nation is at war with Islamic fascists who will use any means to destroy those of us who love freedom, to hurt our nation.’’

Mahdi Bray, executive director of the Muslim American Society Freedom Foundation, said Mr. Bush owed Muslims an apology. “There is no Islamic fascism,’’ Mr. Bray said. “There is no doctrine of fascism in Islam.’’

Esam Omesh, president of the Muslim American Society, said, “We all stand united against the violence and the killing in the holy land.’’

Ramsey Clark, the former attorney general, drew cheers when he said, “We have a solemn obligation to impeach President Bush.’’ Mr. Clark, who has served on the defense team for Saddam Hussein, the former president of Iraq, also advocated the impeachment of Vice President Dick Cheney and Defense Secretary Donald H. Rumsfeld.

Two students from George Mason University in Fairfax, Va. — Ali Khan, 28, a Pakistani-American, and his wife, Afnan Khan, 22, who was born in the United States to Iraqi parents — were less strident. They said they were protesting the death of civilians, especially Lebanese children.

“They are all innocent,’’ Mr. Khan said.