'Merely ... establishing a mechanism within the existing judicial structure is not a credible approach in the eyes of the Kenyan people and the international community,' the statement read.

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.

However, Sheikh Sharif on Tuesday called the meeting a 'great opportunity' for Somalia.

'The meeting shows ... how the international community is ready to support the government,' he told reporters in Mogadishu.

Clinton is then expected to fly to South Africa to pressure new President Jacob Zuma 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.

Clinton then travels to Angola. The southern African nation exports most of its oil to China, but also delivers hundreds of thousands of barrels per day to the US.

Chinese influence in Africa has been growing in recent years as the Asian giant grabs 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.

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 poverty stricken despite massive oil reserves, around eight percent of which are exported to the US.

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