US Secretary of State Hillary Clinton departs this week on a trip that will take her both to Africa's newest nation, South Sudan, and on a visit to the continent's elder statesman, 94-year-old anti-apartheid icon Nelson Mandela.

While Clinton's public focus will be on Africa's democratic achievements and economic potential, the trip also underscores US security ties in the face of an array of growing threats -from Islamist extremists to narcotics cartels.

"The security threats are becoming much more visible and in some ways dangerous than they were before," said Jennifer Cooke, the head of the Africa program at the Center for Strategic and International Studies in Washington. "There are big global issues on the table, and the US does not have the kind of finances available to mount splashy new economic initiatives in Africa."