US President Barack Obama, whose election in 2008 sparked huge expectations in Africa, will hold a summit next week for the continent's leaders.
Invitations were sent to 50 heads of state and government for talks that seem designed to counter China's decade-long surge in investment and trade with the continent.
United States officials said all countries invited to send delegations would do so, most of them headed by presidents but some by vice-presidents, prime ministers or foreign ministers.
Notable absentees will include Egypt's President Abdel-Fattah el-Sisi and Morocco's King Mohammed, who will send envoys, but sub-Saharan Africa will be well represented.
The presidents excluded were Zimbabwe's Robert Mugabe, Sudan's Omar al-Bashir, Eritrea's Issaias Afewerki and the Central African Republic's transitional leader Catherine Samba-Panza.
But, even if Obama's gathering marks the greatest-yet concentration of African leadership in Washington, it is not clear what results can be expected from the three-day summit.
Obama's foreign policy was first marked by a pivot to Asia and a failed bid to "reset" relations with Russia, and he did not make Africa a priority in his first term.
The agenda certainly will include discussion on threats facing the continent. Among them are Islamist group Boko Haram in Nigeria, civil war in South Sudan and attacks by the Somalia militant group Shebab in Kenya.
The US-Africa summit also will have a strong economic aspect, with a programme focused on opportunities for the continent where 60 per cent of the population is under 35 and where growth rates are higher than anywhere else in the world.
The US is third among Africa's major trading partners, far behind long-time number one the European Union, and raw-material-hungry China.
Obama's national security adviser, Susan Rice, has acknowledged that Americans needed to change their "outdated mindset" of the continent.
"Too many Americans still only see conflict, disease and poverty, and not the extraordinarily diverse Africa, brimming with innovation," Rice said.