American tennis star Venus Williams arrived in Nigeria on Tuesday on the first stop of two-country African trip with her sister Serena aimed at promoting women\'s rights. Both sisters are counted among the United States\' most accomplished athletes, sharing 22 major women\'s singles championships between them. Their trip is aimed at promoting \"the role that women play in shifting perceptions and encouraging development at all levels across the African continent,\" said a statement from the Breaking The Mould initiative they are representing. Serena, 31, and Venus, 32, are due to meet the governor of Lagos state, hold a tennis clinic at an exclusive club, visit a puberty education class for girls and play an exhibition match before heading to South Africa on November 2. \"They are coming to Lagos to encourage more women to break moulds that have stood between them and their potentials,\" the statement said. Venus Williams arrived at a hotel in Lagos\'s upmarket Victoria Island district on Tuesday afternoon while her younger sister is due later in the evening, said Lere Ojedokun, of Chain Reactions Nigeria, a communication firm promoting the tour. Gender disparity is an acute problem in Nigeria, Africa\'s most populous country of roughly 160 million people, with the most glaring divides existing in the mainly Muslim north. Worldwide, Nigeria ranks 118 out of 134 countries on the Gender Equality Index, a British Council study released in May said.