Rich countries' pledges of more aid to Africa are undermined by the lack of a delivery timetable which prevents the world's poorest nations from planning development, the International Monetary Fund said on Wednesday. Abdoulaye Bio-Tchane, director of the IMF's Africa department, welcomed the $60 billion pledged last week in Germany by leaders of the Group of Eight (G8) industrialised nations to fight AIDS, malaria and tuberculosis.