In a significant shift, campaigners against the genocide in Sudan’s Darfur region are endorsing a call for world leaders to boycott the opening ceremonies of the Beijing Olympic Games in August. “We are calling on leaders to not sit by as Beijing celebrates itself as an emerging power and international leader while it is underwriting the first genocide of the 21st century,” the executive director of Dream for Darfur, Jill Savitt, told reporters on a conference call yesterday. “Beijing should not be allowed to bask in the warm glow of peace and brotherhood … if China is still underwriting atrocities in Darfur.”

The five organizations that announced backing for a boycott yesterday, Dream for Darfur, the Save Darfur Coalition, the Enough Project, Stand: A Student Anti-Genocide Coalition, and the Genocide Intervention Network, had previously opposed a boycott. Last year, the groups rebuked journalists for reporting that Darfur-related groups were pressing for a boycott. “We do not know of any credible groups working on Darfur that are calling for a boycott of the 2008 Olympics,” they said.

Activists stressed yesterday that the new boycott call was directed only at political leaders and only at the opening ceremonies. The campaigners also said they would withdraw the call if an effective U.N. peacekeeping force is deployed in Darfur.

“We are not asking athletes, spectators, corporate sponsors, or anyone to boycott any of the actually sporting events themselves,” Isaac Shapiro of Save Darfur said. “For the opening day’s ceremonies, similarly, we are not asking athletes not to attend. We are only asking world leaders not to attend.”

Spokesmen at the Chinese consulate in New York and the embassy in Washington did not respond to calls yesterday seeking comment for this article. However, officials in Beijing have reacted abrasively to talk of a boycott.

“If anyone wants to take the world people’s grand event as a stage for political show, he or she has found a wrong place, and will only ask for an insult,” a spokeswoman for the Chinese Foreign Ministry, You Jiang, said, according to the country’s state-run news service, Xinhua.

In an interview, Ms. Savitt noted that the proposal for a boycott of the opening ceremonies seemed to have originated in February with a Dutch lawmaker, Joel Voordewind. He suggested that countries “take part in the games but skip the party beforehand” in order to protest China’s record on a variety of human rights issues.

Ms. Savitt said her group simply had not considered until recently the idea of a boycott limited to the ceremonies. “I think it is an inspired idea. It’s a way to make a gesture without hurting the Olympics. It only punishes China,” she said.

Calls for such a boycott have intensified in recent days after Beijing launched a violent crackdown on protesters in Tibet. Chancellor Merkel of Germany said she would not attend the ceremonies because of the Tibet situation; Prime Minister Tusk of Poland and President Klaus of the Czech Republic also are skipping the event. President Sarkozy of France has said he would consider such a move.

Darfur campaigners may have worried that their concerns would be drowned out if they did not up the ante by joining the boycott call.

Ms. Savitt said her group is coordinating and not competing with activists on issues such as Tibet, Burma, press freedom, and Internet freedom. “We feel the more voices in the chorus addressed to China puts exponentially more pressure on China to take some action,” she said.

White House officials have indicated that President Bush plans to attend the Beijing Olympics and to raise human rights concerns in talks with President Hu of China. A former Republican presidential candidate who ran the Winter Olympics in Salt Lake City in 2002, Mitt Romney, indicated yesterday that he does not believe Mr. Bush should skip the opening ceremonies.

“There are a lot of ways to make statements about what you think about Beijing’s treatment of individuals and particularly those in Tibet, but the opening ceremonies is a tribute to the athletes of the world and particularly the athletes of the home country,” Mr. Romney told CNN. “You know Hitler had games and America sent athletes to Berlin to participate there. … I don’t want, in any way, to compare China to Hitler, or anything of that nature, but what I’m saying is I think the games are about athletes and that we should support our athletes and show recognition of them. That’s why the president would go to Beijing.”

More details were announced yesterday about protests surrounding the visit of the Olympic torch to San Francisco next week. Darfur campaigners have paid to insert hand-held signs reading, “China: Exinguish the Flames of Genocide in Darfur,” in 418,000 copies of this morning’s San Francisco Chronicle. “Every hand-delivered copy will have that sign in it,” a local activist, Martina Knee, said. Onlookers will be encouraged to brandish the signs along the torch route.