Which of the following spearheaded the transformation of the Organization of African Unity into the African Union?

The transformation of the Organization of African Unity into the African Union was spearheaded by Thabo Mbeki, a South African politician who served as the second President of South Africa from 1999 to 2008. Mbeki played a key role in the formation of the African Union, which was established in 2002 to replace the Organization of African Unity. The African Union aims to promote greater unity and cooperation among African countries and to address the continent's social, economic, and political challenges.