From an editorial in the New York Times:
A strong United Nations force is needed to halt the genocide in Sudan’s Darfur region. If it is not sent soon, it may be too late for many thousands of potential victims. The immediate cause of the delay is the refusal by Sudan’s president, Omar Hassan al-Bashir, to agree to a U.N. force, which he preposterously claims would attempt to recolonize his African nation. He is able to get away with this largely because China, a permanent member of the Security Council, continues to protect him with the threat of using its veto.
One reason Beijing stands behind Mr. Bashir is oil. China is trying to diversify its oil sources beyond the crisis-prone Middle East, and Africa is one obvious alternative. Already, some 7 percent of China’s imported oil comes from Sudan.
Another factor is Beijing’s extreme sensitivity to any U.N. encroachments on national sovereignty. China fears that by assenting to U.N. intervention in Darfur over the protests of the Sudanese government, it might open the door to unwanted meddling in its own affairs ” with regard to Tibet, for example. [Full text]