An American president who has "the blood of Africa within me" praised and scolded the continent of his ancestors yesterday, asserting forces of tyranny and corruption must yield if Africa is to achieve its promise.

"Yes you can," Barack Obama declared, dusting off his campaign slogan and adapting it for his foreign audience. Speaking to Parliament, he called upon African societies to seize opportunities for peace, democracy and prosperity.

"This is a new moment of great promise," he said. "To realise that promise, we must first recognise a fundamental truth that you have given life to in Ghana: Development depends upon good governance. That is the ingredient which has been missing in far too many places, for far too long. That is the change that can unlock Africa's potential."

The first United States black president spoke with a bluntness that perhaps could only come from a member of Africa's extended family.

"No country is going to create wealth if its leaders exploit the economy to enrich themselves, or if police can be bought off by drug traffickers," he said

"No business wants to invest in a place where the government skims 20 per cent off the top, or the head of the port authority is corrupt. No person wants to live in a society where the rule of law gives way to the rule of brutality and bribery.

"That is not democracy, that is tyranny, even if occasionally you sprinkle an election in there," he said, "and now is the time for that style of governance to end."

Democratic tradition

He added: "Africa doesn't need strongmen, it needs strong institutions."

Obama was on a 21-hour visit to the West African nation to highlight that country's democratic tradition and engagement with the West. His visit, his first to sub-Saharan Africa as president, was greeted as a "spiritual reunion" yesterday by Ghanian legislators.

Before the flight home, Obama visited Cape Coast Castle, a seaside fortress converted to the slave trade by the British in the 17th century. In its dungeons, thousands of shackled Africans huddled in squalor before being herded on to ships bound for America.

He, his wife Michelle, their daughters and the first lady's mother toured the grounds as a festive crowd of thousands milled outside, pounding drums and dancing in the streets. Obama smiled and waved, pausing after he exited the motorcade, before disappearing with his family and entourage into the courtyard. Michelle Obama is the great-great granddaughter of slaves.

Earlier, people lined the streets, many waving at every vehicle of Obama's motorcade as it headed towards a meeting at Osu Castle, the storied coastline presidential state house, before his speech to Parliament. "Ghana loves you," said a billboard.

The Obama administration sought a wide African audience for the president's speech, inviting people to watch it at embassies and cultural centres across the continent.

The 33-minute address was in part a splash of cold water for Africans who blame colonialism for their problems.

Obama spoke of the indignities visited upon Africans from the era of European rule. He said his grandfather, a cook for the British in Kenya, was called "boy" by his employers for much of his life despite his being a respected village elder. He said it was a time of artificial borders and unfair trade.

But he said the West is not to blame "for the destruction of the Zimbabwean economy over the last decade, or wars in which children are enlisted as combatants". Nor for the corruption that is a daily fact of life for many, he said.

"Africa is not the crude caricature of a continent at perpetual war," he said. Yet for "far too many Africans, conflict is a part of life, as constant as the sun. There are wars over land and wars over resources. And it is still far too easy for those without conscience to manipulate whole communities into fighting among faiths and tribes.

"These conflicts are a millstone around Africa's neck."

The president pledged US partnership in Africa's growth. Specifically, he said he would make sure US aid gets to the people who need it most, such as farmers and entrepreneurs, not Western consultants and administrators.

That's why $3.5 billion in food assistance will focus on new methods and technologies for farmers, instead of simply sending US goods to Africa, he said.