When Simon Deng was eight years old, Arab marauders from the north of his native Sudan sacked his village and burned the tribal elders alive. The next year he was kidnapped and given to a Muslim family as their slave. His masters beat Mr. Deng, a black man from southern Sudan, forcing him to sleep with animals and overworking him to exhaustion. They promised him they would stop if he forsook Christianity, converted to Islam, and took an Arab name. But he never did.

“You are looking at a human being who, at one time, he was a gift,” Mr. Deng said. “I was constantly under terror. I would cry for mercy, but always that mercy is not there.”

After 3 1/2 years of slavery, Mr. Deng recognized a member of his tribe in the city of Kosti by the traditional marks on his forehead, known as shilluk. The man arranged to smuggle him back to his family. Mr. Deng promptly had his own shilluk put in.

Now 45 years old, Mr. Deng told his story yesterday at the Elim Christian Academy on Staten Island to gather support for a proposed 22-day Freedom Walk to Washington, D.C. from New York City, to raise awareness of what many call genocide and to pressure the American government to stop it. Mr. Deng and others will begin the walk on March 15 outside the U.N.’s headquarters, and end with a rally on April 5 outside the Capitol building.

Mr. Deng immigrated to New York 15 years ago and has since become an American citizen. A former swimming champion in Sudan, he now works as a lifeguard at Coney Island.

Though the latest atrocities in Darfur have provoked international calls for action, Mr. Deng said the problem was much greater, describing more than 50 years of slaughter by government-funded Arab militias across Sudan.

At first, the killings were religiously motivated, he said – the Muslim government declared jihad on any Sudanese who did not convert to Islam and follow Shariah law. The ongoing slaughter, he said, amounts to racial and cultural cleansing as the now mostly Muslim black Sudanese are murdered, children enslaved, and women raped to change the race of their offspring.

“Those who cannot speak for themselves are being butchered and sold and bought into slavery. Can we do something?” Citing the Armenian massacre of 1915, the Holocaust, Pol Pot’s atrocities in Cambodia, and the slaughter in Rwanda, he asked: “As human beings, are we going to repeat the same mistake as we always do?”

American action is the only solution, Mr. Deng added. “I will be the last man alive to trust the United Nations.”