US President Barack Obama Tuesday vowed an urgent effort to bring electric power to the impoverished heart of Africa, as he wrapped up a week-long journey through the continent in Tanzania.
Obama also performed a sombre double act with George W. Bush, linking up to remember victims of an embassy bombing in Dar es Salaam in 1998, a day after praising his predecessor's AIDS programme as a "crowning achievement."
The US leader travelled to the Ubungo power plant, repaired with US funds, to bemoan the plight of 70 percent of Africans who lack reliable access to electricity, and to promote his new $7 billion effort to help.
"All of us have to feel a sense of urgency. If we are going to electrify Africa, we've got to do it with more speed," Obama said.
The plan, dubbed "Power Africa," leverages loan guarantees and private sector finance and aims to double access to electricity in sub-Saharan Africa, where more than two-thirds of the population lives in the dark.
It will initially be targeted on Ethiopia, Ghana, Kenya, Liberia, Nigeria and Tanzania.
Obama also had fun Tuesday trying out a device known as a "Socketball" which hides a generator inside a football and can be used to power a light or a cellphone using kinetic energy stored during a kick around.
The US leader juggled the ball on his foot and his head, and then demonstrated how it could be hooked up to a cellphone.
"I thought it was pretty cool," he said.
"You can imagine this in villages all across the continent."
Earlier, in an unusual meeting of the exclusive US presidents club on foreign soil, Obama met Bush, pioneer of the President's Emergency Plan for AIDS Relief (PEPFAR) which saved millions of lives, and also treats tuberculosis and malaria.
Democrat Obama and Republican Bush bowed their heads at a stone memorial to the 11 people killed in 1998 when Al-Qaeda bombed the US embassy in Dar Es Salaam.
They stood side by side as a US Marine fixed a red, white and blue wreath on a stand, and then greeted American and Tanzanian guests.
Bush, who also visited Zambia, was in Tanzania for a forum of regional First Ladies, hosted by his wife Laura, also attended by Michelle Obama.
Obama, Michelle and their two daughters later took off aboard Air Force One to head back to Washington, ending a tour that also included Senegal and South Africa, dominated by the fading health of anti-apartheid icon Nelson Mandela.
He repeatedly urged Africans to embrace the unifying legacy and singular crusade for political change embodied by Mandela, on a continent scarred by years of war and poor governance.
Delighted crowds had thronged Obama when he arrived in Tanzania on Monday, to drive home the message that he wanted to help "Africa to build Africa, for Africans."
As well as the power plan, Obama pushed initiatives on his trip to boost regional trade with America, to tear down customs and border logjams delaying exports and to save Africa's endangered elephants and rhinos.
Tanzania is the kind of African democracy, aided by US health and infrastructure programs, that Washington wants to see duplicated in the region.
It did not escape Washington's notice that Xi Jinping included Tanzania on his first foreign trip as president of China in March.
Throughout his Africa journey, Obama implicitly touted US-style investment and partnership as superior to Beijing's own Africa push, arguing US firms do more to build local economic capacity.
Obama left Africa more convinced that the region's future was bright.
"Even as this continent faces great challenges this is also a moment of great promise for Africa," Obama told businessmen in Tanzania Monday.
He also renewed his promise to visit Kenya, after bypassing his late father's homeland on this African tour, as President Uhuru Kenyatta awaits trial at the International Criminal Court over 2007-2008 election violence.
"I am going to be president for another three and a half years," Obama said at a town hall meeting in Soweto that was broadcast to several African nations, including Kenya.
"If, in three years and seven months, I am not in Kenya, then you can fault me for not following through on my promise."