Her visit to Ghana, the first stop on an African tour that will also take her to Tanzania and Zambia, is part of a charm offensive by Washington as it seeks to counter-balance the growing influence of China and Russia on the continent.

Standing in front of Black Star Gate, a monument built on the site where Ghana declared independence from Britain in 1957, Harris started by noting that by the middle of the century, one in four people in the world will be African.

"That of course means what happens on this continent impacts the entire world," she said.

Citing examples such as the pioneering of mobile phone payments in Kenya or healthcare deliveries by drone in Rwanda before such services existed in the United States, Harris said innovation would be key to Africa's future success.

"We must invest in the African ingenuity and creativity which will unlock incredible economic growth and opportunities, not only for the people of the 54 countries that make up this diverse continent, but for the American people and people around the world," she said.

Turning to the theme of women's empowerment, Harris underlined deep gender disparities in Africa, saying the United States would work alongside African partners to close those gaps.

"On the continent of Africa we know women grow a majority of the food, yet they are less likely to own the land they farm. They represent a majority of frontline healthcare workers, but face disparities in health outcomes," she said.

"Women are entrepreneurs, yet have limited access to capital and markets. They are peacemakers and bridge builders, yet continue to be under-represented at the table where decisions are made."

To cheers, she said that the economic empowerment of women would benefit not only themselves but also their children, families, communities and the entire economy.

The two other areas where Harris said the United States would work with African partners to make progress were digital inclusion and good governance and democracy.

She described the latter as "a work in progress, including in my own country", an apparent allusion to the turbulence seen in U.S. politics and elections in recent years.

(Writing by Estelle Shirbon, editing by Giles Elgood)

By Cooper Inveen