US Secretary of State Hillary Clinton is in Uganda and will spend a night in the capital, Kampala before a visit to the world's newest nation South Sudan, locked in a crippling border and oil dispute with Sudan.

She flew out of Senegal on Thursday headed for Uganda.

Her 11-day tour of seven African nations focuses on President Barack Obama's new Africa strategy of promoting development by stimulating economic growth, advancing peace and security and strengthening democracy.

In Senegal, Clinton hailed the West African nation as an example that "democracy can prosper on the continent".

She said she had a "productive, comprehensive" discussion with President Macky Sall.

"I want to thank him for taking time to discuss a number of issues - economic issues, regional, security issues, issues that the United States is very committed to assisting Senegal on addressing."

Clinton will spend one night in Kampala, the Ugandan capital which has been hit for the first time. She then visits South Sudan, which celebrated its first anniversary on July 9 and where she will meet with President Salva Kiir.

The world's newest nation, in whose birth the United States played a major part, has yet to agree on its border with the rump state of Sudan and settle a crippling dispute on oil revenues.

The UN Security Council has given the two states, who this year came close to all-out war, until Thursday to reach a peace deal or face sanctions.

"We are encouraging both sides, South Sudan and Sudan, to effectively negotiate the differences between them," said a high-ranking official from the state department.

"Both countries are in a non-work spiral as a result of their political differences and as the result of the cut-off in oil... Our desire is to see all of these issues negotiated out."

Clinton will also visit Kenya, Malawi, South Africa and finish her trip by attending the state funeral of Ghana's late president John Atta Mills on August 10.

AFP