US Secretary of State Hillary Rodham Clinton was due to touch down in Kenya Tuesday on the first leg of a seven-nation African tour US officials say demonstrates Africa is a foreign policy priority for the Obama administration.

Clinton's tour comes just three weeks after President Barack Obama visited Ghana, his first trip to Africa as president. According to Assistant Secretary of State for African Affairs Johnnie Carson, Clinton will pick up on many of the same themes.

"[The] trip follows the themes laid out by President Obama ... supporting strong and sustainable democratic governments; promoting sustainable economic development ... assisting in the prevention, litigation, and resolution of conflicts around Africa," Carson told journalists prior to departing with Clinton.

Clinton is due to open the African Growth and Opportunity Act (AGOA) Forum in Kenyan capital Nairobi on Wednesday. AGOA provides sub-Saharan African nations liberalized access to US markets.

However, the US's top diplomat is then expected to address more thorny issues.

The secretary will visit several countries with major human rights problems, such as the Democratic Republic of Congo and Nigeria, and she is under pressure to bring the governments to task.

"The US rightly wants to promote Africa as a place of great opportunity, but Africans will be unable to realize their potential if their human rights are denied," said Georgette Gagnon, Africa director at New York-based Human Rights Watch. "Secretary Clinton should make this connection clear."

Clinton's first delicate task is expected to come when she meets Kenyan President Mwai Kibaki and Prime Minister Raila Odinga and presses them to create a new constitution.

Obama's decision to ignore Kenya, the birthplace of his father, on his first trip to Africa was seen as a coded message to the Kenyan government to bring to justice those responsible for early 2008's bloody post-election violence.

Over 1,500 people died in tribal clashes that followed Odinga's claims that Kibaki stole the December 2007 presidential elections, yet Kenya has failed to create a local tribunal to try those responsible for orchestrating the violence.

While still in Kenya, Clinton is also due to meet Somali President Sheikh Sharif Sheikh Ahmed, whose government is wobbling under a fierce onslaught from Islamist insurgents believed to have close links with al-Qaeda.

The US has already provided military supplies to the Somali government, but Carson said no further assistance was expected to be pledged at the meeting.

Clinton is then expected to fly to South Africa to pressure new President Robert Mugabe into forcing Zimbabwe's Robert Mugabe to respect the country's power-sharing deal.

She is also expected to discuss the reactivation of a bilateral US-South Africa commission to govern relations.

In Angola, which is Africa's second-largest crude oil exporter, Clinton is expected to meet the energy minister. Angola exports most of its oil to China, but the southern African nation also delivers hundreds of thousands of barrels per day to the US.

China's influence in Africa has been growing in recent years as it leads the way in grabbing a slice of Africa's mineral wealth, but Carson denied that Clinton's visit was in any way aimed at combating China's growing influence.

The next planned stop is the Democratic Republic of Congo, where Clinton is expected to highlight US commitment to ending gender-based violence by meeting victims of rape.

Rape has been widespread in the DR Congo during over a decade of civil strife that has claimed the lives of over 5 million people.

Energy is then expected to be back on the agenda during a planned visit to Nigeria, Africa's largest oil-producer and most-populous nation.

The country of around 150 million people is largely stricken despite massive oil reserves, around 8 per cent of which are exported to the US.

Corruption and poor governance are blamed for the economic disparities, and Clinton is expected to address these issues in meeting with the government.

The final two stops are expected to be Liberia, which is still recovering from a long civil war, and the stable Cape Verde.