NEW : He gives former slave trade post a powerful reminder to keep focus on human rights . Obama calls for banning slavery ; Senegalese President Sall says no . `` Obviously , for an African-American , an African-American president , to be able to visit this site , I think , gives me even greater motivation in terms of human rights around the world , '' Obama said . He 's encouraging U.S. investment , addressing development issues , promoting democracy in Africa . ' Mandela 's legacy has linger ` ` throughout the ages , '' Obama says .
NEW : He gives former slave trade post a powerful reminder to keep focus on human rights . Obama calls for banning slavery ; Senegalese President Sall says no . He 's encouraging U.S. investment , addressing development issues , promoting democracy in Africa . ' Mandela 's legacy has linger ` ` throughout the ages , '' Obama says .