By Andrew Quinn
DAKAR (Reuters) - U.S. Secretary of State Hillary Clinton arrived in Senegal on Tuesday, beginning a trip that will take her both to Africa's newest nation South Sudan and on a private visit to the continent's elder statesman, 94-year-old anti-apartheid leader Nelson Mandela.
While Clinton's public focus will be on Africa's democratic achievements and economic potential, the trip also underscores U.S. security ties in the face of growing threats - from Islamist militants 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 U.S. does not have the kind of finances available to mount splashy new economic initiatives in Africa."
Clinton's trip - potentially her last as America's top diplomat - will take her to South Sudan on Friday, where she will be the most senior U.S. official to visit since the country declared independence in July 2011.
Further stops include Uganda, Kenya, Malawi and South Africa, where Clinton will stop in Mandela's home village of Qunu on Monday for a private meeting with the revered liberation leader who has quietly faded from public view in his formal retirement.
Clinton will conclude the trip on August 10 at the funeral of Ghana's late President John Atta Mills, whose sudden death on July 24 has been followed by a smooth transition in one of Africa's most stable democracies, U.S. officials said.
Throughout the trip, Clinton is expected to highlight U.S. programs on development, education and HIV/AIDS -- long the backbone of U.S. engagement with Africa -- as well as U.S. economic interest in a continent whose rich resources and enviable growth rates have drawn rival suitors including China and India.
She will also likely emphasize projects for women and girls, one of her central themes in a job she says she will leave in January even if President Barack Obama is elected to a second term.
But Clinton's visit is also part of a U.S. push to broaden security partnerships with key countries such as Uganda and Kenya -- ties that are growing fast despite sometimes serious U.S. concerns over democratic governance.
Obama laid out his policy for Africa in a speech in Ghana in July 2009, saying the United States stood ready to help African nations as they work to improve governance, fight corruption and resolve regional conflicts.
His speech led to widespread hopes on the continent that the first U.S. president with African roots would follow through with new policies to help achieve those goals.
But his administration has not launched major new initiatives such as the Clinton-era trade pact that granted tax breaks to African goods or President George W. Bush's AIDS initiative of 2003, which committed billions of dollars to the fight against HIV/AIDS on the continent.
"Africans will always see Obama as one of our own, so we are reluctant to criticize," said Mwangi Kimenyi, a Kenyan academic and director of the Africa Growth Initiative at the Brookings Institution.
"But it turns out our expectations for the president were a bit overrated and unrealistic. He could have been more courageous and done more."
The White House last month released a strategy paper on Africa, repeating its commitment to strengthening democracy and spurring economic growth but lacking a single signature project which could cement Obama's Africa legacy.
Instead, attention has focused on AFRICOM, the unified U.S. Africa Command that the Pentagon established in 2007. It is playing an increasingly important role as the United States pumps resources into training African militaries.
Washington has reacted with increasing alarm as militant groups such as Somalia's al Shabaab, Nigeria's Boko Haram and al Qaeda's African wing based in the vast Sahel region open new fronts to advance Islamic extremism.
Concern over the Sahel has spiked since March when a coup in Mali opened the door to al Qaeda-linked Islamists in the north of the country, leading some analysts to say the lawless region could become an "African Afghanistan."
J. Peter Pham, director of the Africa program at the Atlantic Council, said Washington's emphasis on security, coupled with the lack of new economic initiatives, had shifted the balance in U.S. ties with Africa.
"It is militarization by default," Pham said. "Part of the reason is the U.S. interest in fighting al Qaeda, and part of it is because of the weakness of our African partners which are unable to contain these threats themselves."
The diverging U.S. priorities in Africa will be on display when Clinton visits Uganda, frequently cited as both a strong security partner and a country where democratic gains are under threat.
Ugandan President Yoweri Museveni's troops make up most of the African Union force attempting to stabilize Somalia and are now working with 100 U.S. military advisers to track down fugitive warlord Joseph Kony, perhaps Africa's most wanted man.
But opponents also criticize Museveni for what they say is his increasingly authoritarian rule, and the United States has joined other donor nations voicing concern over proposed tough new laws on homosexuality that have sparked an outcry among gay rights advocates.
The State Department said Clinton would use her visit "to encourage strengthening of democratic institutions and human rights, while also reinforcing Uganda as a key U.S. partner in promoting regional security."
(Editing by Mohammad Zargham and Michael Roddy)