Some 700 people took part in the Washington rally, at which a petition demanding U.S. action and bearing tens of thousands of signatures was unfurled, said Ann-Louise Colgan, director of policy analysis at Africa Action, one of the event's organizers.

''As Americans struggle to cope with the President's failure of leadership on the domestic front in the horrific aftermath of Hurricane Katrina, we must also condemn the President's failure of political leadership on the international front, where he has failed to act to stop the ongoing genocide in Darfur and the death toll continues to mount,'' said Salih Booker, the organization's executive director.

Separately, the Sudanese government and two main rebel groups from Darfur said Thursday they would attend peace talks scheduled to resume Sep. 15 in Nigeria's capital, Abuja.

Violence in Darfur, now in its third year, has killed more than 400,000 people and forced 2.5 million of the region's 5.5 million people to flee their homes and villages, U.N. agencies and advocacy groups have estimated.

Relief workers also have been caught up in the fighting. The United Nations Mission in Sudan (UNMIS) said Tuesday it had received fresh reports of fighting between rebel groups and the nomadic Janjaweed militia, looting of humanitarian assistance, and attacks on villages.

''The combat between the Janjaweed and the Sudanese Liberation Army (SLA) has been taking place in the Jabal Moon hills in North Darfur,'' UNMIS said in a statement, ''but the situation in West Darfur is most troubling, following two attacks last week on humanitarian convoys sent in by non-governmental organizations (NGOs).''

The death toll could exceed one million people by the end of the year unless bold steps are taken to rein in the conflict between rebel groups of African descent and Arab militias that the regime in Khartoum stands accused of arming and abetting, Africa Action warned. It has urged Washington to push for the deployment of an international peacekeeping force and has demanded that Africa Union (AU) peacekeepers be given a political mandate to intervene in the fighting to protect civilians.

The fighting started over rebels' claims that the Sudanese government had deliberately neglected Darfur, starving it of basic services and development money. It has been compounded by competition for control of local oil, gas, and mineral resources.

Even as government and rebel forces implement a peace process in the country's south, the Khartoum regime appears to be girding for new violence in eastern Sudan, where local populations also are rebelling against the government, according to Africa Action.

In 2000, the group was among the first to warn of what it then saw as an impending crisis in Darfur.

Secretary of State Condoleezza Rice visited Sudan in July and urged the government to end the violence in Darfur, a region about the size of Texas.

However, U.S.-Sudanese intelligence cooperation in what the White House calls its ''war on terror'' and prospects for peace in war-torn southern Sudan dominated Rice's talks with President Omar Hassan Ahmad al-Bashir and senior government officials.

Washington also has pledged to help airlift AU troops from their home countries to Sudan.

Even so, speakers at Thursday's rally chided the White House for what they said amounted to scant lip service. They renewed demands for urgent action to protect Darfur's civilians and to mobilize a multinational intervention to support the AU, Africa's equivalent of the European Union.

''We call on President Bush, one year after he recognized the genocide in Darfur, to take decisive and effective action to end the violence that is brutalizing innocent civilians in Darfur,'' said David Rubenstein, coordinator of the 134-organization Save Darfur Coalition, which claims a combined membership of more than 130 million Americans.

Thursday's event was organized by Africa Action, American Jewish World Service, Armenian National Committee of America, Evangelical Lutheran Church of America, Faithful America, Greater Washington Jewish Task Force on Darfur, NAACP, National Council of Churches, Religious Action Center of Reform Judaism, Save Darfur Coalition, Sojourners, STAND, Sudan Peace Advocates Network, TransAfrica Forum, and the United Methodist Church.

Anti-genocide activists also have been pressing U.S. television networks to increase coverage of the Darfur situation, described by the United Nations as the world's worst humanitarian crisis.

The campaign--run by the American Progress Action Fund and the Genocide Intervention Fund--asks networks to ''be a witness'' to the genocide in Darfur.

Organizers said they hoped increased coverage would move voters to exert pressure on elected officials.

''Television has told us stories of important human brutality before, and Americans have responded by demanding action from our elected representatives,'' the campaign said in a statement citing examples including the civil rights struggles of the 1950s and 1960s and the Ethiopian famine of the 1980s.

Last year, the ABC, CBS, and NBC network nightly newscasts aired a total of only 26 minutes on Sudan, according to the Tyndall Report, which monitors major broadcasters. ABC devoted 18 minutes to Darfur coverage, NBC five, and CBS only three. By contrast, lifestyle doyenne Martha Stewart's legal woes received 130 minutes of nightly news coverage.

A U.N. commission concluded last January that crimes against humanity--but not genocide--had occurred in Darfur. In April, the world body passed a resolution referring cases of alleged atrocities since July 1, 2002 to the International Criminal Court.

U.N. Secretary-General Kofi Annan then handed the names of 51 people suspected of war crimes and atrocities in Darfur to the court. The list included Sudanese government and army officials as well as militia and rebel leaders.