WASHINGTON – Thousands of people joined celebrities and lawmakers at a rally yesterday urging the Bush administration to use its political muscle to help end genocide in Sudan’s Darfur region.

“Not on our watch,” the crowd began chanting as a parade of speakers lined up for their turn on a stage on the National Mall, the Capitol serving as a backdrop.

“The personal motivation for a lot of us is the Holocaust,” said Boston-based Rabbi Or Rose of Jewish Seminarians for Justice. “Given our history and experience, we feel an obligation to stand up and speak out.”

The organizers’ permit estimated a turnout of 10,000 to 15,000 for the rally, one of several planned in American cities over the weekend over what the United Nations has termed the world’s worst humanitarian disaster.

“It is the socially responsible, good conscience thing to do,” said Ron Fisher, who took a pre-dawn bus from Cleveland with his 15-year-old daughter Jordyn to attend the demonstration. “It’s an opportunity to show my daughter what people do when they care about something.”

The U.S. Park Police, which does not issue crowd estimates, reported no arrests. “It’s a large crowd. I think they have a really good turnout,” Sergeant Scott Fear said.

The event attracted high-profile speakers from the worlds of screen, athletics, religion, and politics: actor George Clooney, just back from a trip to Africa; Senator Obama, a Democrat of Illinois; House Democratic leader Nancy Pelosi of California; Nobel Peace Prize winner Elie Wiesel; Olympic speedskating champion Joey Cheek, who donated his bonus money to projects in war-torn Darfur, and Roman Catholic Cardinal Theodore McCarrick, archbishop of Washington.

Refugee Hassan Cober said he was forced to leave his family and flee Sudan four years ago after many were killed and raped in his village. He urged America and the United Nations to act quickly, saying he had no idea where his family was or if they were OK.

“We need deeds, not words,” said Mr. Cober, who now lives in Portland, Maine. “They need to come to Darfur today, not tomorrow, because what is going on is a disaster.”

Secretary of State Rice, in a broadcast interview, noted developments yesterday in Nigeria, where Sudan’s government said it was ready to sign a peace agreement to end the bloodshed. Rebels, however, rejected the draft deal.

“Obviously a peace agreement would be a very important step forward in getting this done,” Ms. Rice said on ABC’s “This Week.”

Years of fighting between ethnic groups and Arab militias in western Sudan have left at least 180,000 people dead and about 2 million homeless. Amid the talks, the plight of 3 million refugees in Darfur has worsened. The U.N. World Food Program said Friday that it was cutting rations in half, citing a lack of funds.

President Bush met with Darfur advocates at the White House on Friday and lent his support to the weekend rallies. “For those of you who are going out to march for justice, you represent the best of our country,” Mr. Bush said.