The head of the new US military command for Africa (Africom) has told the BBC it has "no hidden agenda".
General William Ward said the command would not be used to gain control of African natural resources such as oil.
He also dismissed fears that the US intended to build large military bases on the continent.
Only one country, Liberia, has offered to host Africom, which is coming into full operation at its headquarters in the German city of Stuttgart.
General Ward said the location of the headquarters, for its 1,300 military and civilian personnel, was less of a concern, given the size of the African continent.
The BBC's Adam Mynott says the creation of Africom is a recognition by the US that Africa and security issues on the continent are now a priority.
It reflects concerns about tackling Islamist extremism, securing oil supplies, and countering Chinese influence in Africa, he says.
But its creation has been met with considerable scepticism, our correspondent says.
However General Ward said Africom did not intend to help the US get control of more of Africa's oil and other resources.
"There is no hidden agenda. It is about working with the African nations to help them build their capacity," the general told the BBC's World Today programme.
He said it was a "myth" and "absolutely not the case" that the command was going to build big bases in Africa.
"We will do those things in partnership with our African friends," he said.
"Where we bring in, for instance, trainers or other forms of military support and assistance there, they are only so long as is required to conduct the specific training that we've been asked to do or to conduct the specific activities."