US President Barack Obama on Friday played down talk of great power rivalry in Africa, welcoming investment by the likes of China and rejecting the idea of Cold War-style proxy economic duel.

But Obama, speaking aboard Air Force One as he flew to Johannesburg from Dakar, did make a strong case for the US model of investment, which prioritises local capacity building, democracy and good governance.

"I think it's a good thing that China and India and Turkey and some of these other countries -- Brazil -- are paying a lot of attention to Africa," Obama said.

"This is not a zero-sum game. This is not the Cold War. You've got one global market, and if countries that are now entering into middle-income status see Africa as a big opportunity for them, that can potentially help Africa."

Obama said the model was "greatly preferable" for a country like Senegal, where he started his three nation tour and announced a new partnership to boost agriculture and fight poverty and hunger.

"In my discussions, a lot of people are pleased that China is involved in Africa.

"On the other hand, they recognise that China's primary interest is being able to obtain access for natural resources in Africa to feed the manufacturers in export-driven policies of the Chinese economy.

"And oftentimes that leaves Africa as simply an exporter of raw goods, not a lot of value added -- as a consequence, not a lot of jobs created inside of Africa, and it does not become the basis for long-term development."

Chinese trade with Africa soared to $200 billion last year.

In March, China's new President Xi Jinping visited Africa, as well as Russia, on his first foreign trip signing a raft of business and energy deals signalling Beijing's intent to deepen ties further.

Obama said that the involvement of emerging powers in Africa was a sign of the continent's economic potential and new vitality and also a warning to the United States that it cannot afford to stay on the sidelines.

Obama's tour, also including Tanzania, is meant to make up for lost time, as the son of a Kenyan who became the first black US president made only one brief stop in sub Saharan Africa, in Ghana, during his first term.

He is bringing with him some of his top economic advisors and CEOs and executives from blue chip American firms to drive new American investment and business links with the continent.

On Saturday, top aide Valerie Jarrett and US Trade Representative Mike Froman will hold a breakfast meeting with executives from groups including Coca Cola, Ford Motor Company, The Development Bank of South Africa, The Carlyle Group, Goldman Sachs International and the African Finance Corporation.

"One of the main things that we want American companies to see is that Africa is ready to do business and that there's huge potential there," Obama told reporters.

"What African countries have to do ... is ensure that there's stability and good governance so that American companies can reduce some of those risks that have nothing to do with business and have to do with, will they be able to get their profits out?"