Together with Nobel Peace Prize recipient Elie Wiesel, Clooney urged members of the U.N.'s Security Council to help end atrocities in the region.
U.N. staffers gathered outside the basement meeting room Thursday to catch a glimpse of the actor burst into applause as Clooney, dressed in a sober suit and tie, arrived with Wiesel for the informal briefing organized by the Elie Wiesel Foundation for Humanity.
Inside, Clooney told the U.N.'s most powerful body that it must send replacements for the African Union's 7,000 peacekeepers in Darfur when its mandate expires at the end of the month. If it did not, aid workers would have to leave and the 2.5 million displaced people who depend on them would die.
"After Sept. 30 you won't need the U.N. You will simply need men with shovels and bleached white linen and headstones," the 45-year-old actor warned.
The Sudanese government has refused to approve the replacement of African Union peacekeepers by a U.N. force, saying it would violate the country's sovereignty.
More than 200,000 people have been killed and over 2 million have fled their homes since 2003 when ethnic African tribes revolted against the Arab-led Khartoum government.
A May peace agreement signed by the government and one of the major rebel groups was supposed to help end the conflict in Darfur. Instead, it has sparked months of fighting among rival rebel factions that has added to the toll of the dead and displaced.
"The United States has called it genocide," Clooney told council members. "For you it's called ethnic cleansing. But make no mistake — it is the first genocide of the 21st century. And if it continues unchecked it will not be the last."
In stark words he told the U.N. diplomats: "In many ways it is unfair, but it is nonetheless true that this genocide will be on your watch. How you deal with it will be your legacy, your Rwanda, your Cambodia, your Auschwitz."
"We were brought up to believe that the U.N. was formed to ensure that the Holocaust could never happen again. We believe in you so strongly. We need you so badly. If not the U.N., then who?" Clooney asked.
Wiesel also urged council members to send peacekeepers. "You are the last political recourse of Darfur victims and you can stop it."
"Remember Rwanda?" Wiesel said. "I do. Six hundred thousand to 800,000 human beings were murdered. We knew then as we know now they could have been saved and they were not."
Clooney and Wiesel gave a brief press conference after the meeting ended. Clooney tried to hang back, saying, "We'll let the Nobel Prize winner do the talking," but most of the questions were directed at him.
Clooney said had he chosen this cause because it was "the first genocide of the 21st century."
Wiesel, however, stopped short of calling the killings in Darfur a genocide. "I call it a process of genocide," he explained. "If we let it continue it will end in genocide. Genocide is not a one-time action. It's a process. They began a process. And therefore I think the United Nations will have to accept that definition. I am usually very, very careful in using that word."
Clooney and his journalist father, Nick Clooney, spent five days in Darfur in April, gathering personal stories of the death and suffering that has ravaged the African region. Both Clooneys have continued working since their return to publicize the plight of refugees.
The actor told reporters at the U.N.: "Of course you are emotionally attached once you are there. It's one thing to talk about murder and rape and justice and it's another thing to see it on a mass scale and see how cruel people can be to one another."
Wiesel, who survived the Nazi death camps at Auschwitz and Buchenwald during World War II, has worked for human rights in many parts of the world and was awarded the Nobel Peace Prize in 1986.
"Because we went through that period of suffering and humiliation we must do something so that other people should not go through any suffering and humiliation," he said.