UN: Genocide? What Genocide?

Amazingly, the United Nations has decided that there is no genocide in Darfur, Sudan. Dictionary.Com defines genocide as "The systematic and planned extermination of an entire national, racial, political, or ethnic group." Currently, Janjaweed militia groups - Arab Muslims - are seeking the destruction of the villages and societies of native Christian Africans. The militias are systematically attacking villages, raping the women, and driving out any survivors. Sounds like genocide to me. But not to the U.N. After all, if it was genocide, they might have to do something.