 Complete the following phrase:  Despite policy disagreements, the U.S. has been a major donor of humanitarian aid to Sudan throughout the last quarter of the 20th century. The U.S. provided assistance for resettlement of refugees following the 1972 peace settlement that brought the First Sudanese Civil War with the south to an end. The U.S. was also a significant source of aid in the March 1989 Operation Lifeline Sudan, which delivered 100,000 metric tons of food into both government and SPLA-held areas of Sudan, averting widespread starvation. In 1991, the U.S. made large donations to alleviate food shortages caused by a two-year drought. In October 1997, the U.S. imposed comprehensive economic, trade, and ficial sanctions against Sudan. However, during another drought in 200001, the U.S. and the broader international community responded to avert mass starvation in Sudan. In 2001, the Bush Administration named a Presidential Envoy for Peace in Sudan to explore what role the U.S. could play in ending 