"And the evidence of the relations between Africa and the United States is personified through his (Tillerson's) visit; I believe reasonably this partnership has produced results". He said there was no monopoly on investment in African countries.
Geng said China's financing support to Africa was mainly in infrastructure and production areas.
"We have done our best to avoid increasing Africa's debt burden", he said.
The United States says African countries could lose sovereignty if they are not careful about the loans they receive from China. Tillerson, sitting beside the Chairperson to the African Union, avoided directly answering questions about President Trump's alleged vulgar language in a discussion about immigrants from African nations - though a journalist bluntly asked him if he agreed with Mr. Trump's controversial comments.
The complex was funded and built by China and is seen as a symbol of Beijing's thrust for influence and access to the continent's natural resources.
Tillerson reiterated previous calls for African states to cut ties with North Korea. North Korea has more than a dozen embassies on the continent. Mr. Trump's remarks from January are, "an incident of the past", he said.
Later in Djibouti, Tillerson attempted to differentiate between negotiation and talks.
The US diplomat, who arrived in Nairobi on Friday, had been due to visit the AIDS-relief program PEPFAR on Saturday and also attend a ceremony marking 20 years since Al-Qaeda bombed the US embassies in Kenya and Tanzania, killing 224 people.
Earlier, Tillerson announced $533 million in food security assistance for Somalia, South Sudan, Ethiopia and the Lake Chad region. And he said he was "looking forward to more opportunities to trade" with Kenya.
He also told the Kenyan government that it should not threaten the courts.