Margaret Warner talks to U.N. Ambassador Susan Rice about the ethnic tension in Sudan ahead of an important referendum on whether the oil-rich South should secede.

As flooding continues to worsen in southern Pakistan, U.S. officials said that insurgents may be targeting flood relief workers there. Meanwhile, the United Nations made a plea for more aid for victims. Jim Lehrer has more.

An American soldier in Iraq opened fire on his comrades, killing five and injuring three others, and volunteers in Sri Lanka dug mass graves after two days of deadly shelling in which up to 1,000 civilians were killed.