Hillary Clinton, the US secretary of state, has urged African leaders to embrace democracy and partnerships with responsible foreign powers as a means to improving their living standards, as she launched a seven-nation Africa tour.
"There are still too many Africans living under autocratic rulers who care more about preserving their grip on power than promoting the welfare of their citizens," Clinton said at a university in Senegalese capital, Dakar.
"The old ways of governing are no longer acceptable. It is time for leaders to accept accountability, treat their people with dignity, respect their rights and deliver economic opportunity. And if they will not, then it is time for them to go."
Speaking at Dakar's University of Cheikh Anta Diop, she said that coups and power grabs had reduced the count of full electoral democracies on the continent to 19 in 2012 from 24 in 2005.
Clinton challenged Africa's elite to fully respect human rights and warned of the consequences of rampant abuses, corruption and intolerance that breed contempt and contribute to instability.
"There are still too many places in the region and across the continent where democracy is threatened, where human rights are abused, and the rule of law is undermined,'' she said.
The secretary of state praised her hosts in Senegal for overcoming tensions to hold elections in March that saw President Macky Sall defeat long-time incumbent Abdoulaye Wade, reinforcing the country's credentials as one of the most stable democracies in the continent.
But she said democracy was too often on the back foot in Africa despite decades of economic progress.
Constitutional order has been restored in Niger and Guinea following recent coups, while Benin, Cape Verde, Liberia, Nigeria, Zambia and Togo have all held credible elections over the past year.
But Clinton warned that sobering alternative paths were being taken by Mali and Guinea-Bissau, saying the latter risked becoming "dependent" on Latin American drug traffickers.
Clinton said the US would stand by African reformers and indirectly took on China. Beijing has been criticised for ignoring human rights concerns, local laws and environmental regulations as it boosts investment in Africa in search of energy and resources to fuel its exploding economy.
By contrast, she said the US is committed to "a model of sustainable partnership that adds value, rather than extracts it'' from Africa.
"The days of having outsiders come and extract the wealth of Africa for themselves leaving nothing or very little behind should be over in the 21st century,'' she said.
Without mentioning China by name, she maintained that unlike other countries, "America will stand up for democracy and universal human rights even when it might be easier or more profitable to look the other way, to keep the resources flowing".
Clinton said that US President Barack Obama, in his landmark speech on Africa in Ghana in 2009, had pledged that the US would offer "partnership, not patronage".
Clinton's comments follow a China-Africa summit last month at which Chinese President Hu Jintao pledged $20bn in credit to African governments over the next three years to support infrastructure, agriculture, manufacturing and small business growth.
Her 11-day tour will also take her to South Sudan, Uganda, Kenya, Malawi, South Africa and Ghana.
On Friday, Clinton will travel to South Sudan, becoming the most senior US official to visit the country since it became independent last year.
In Uganda, where the US has recently deployed a small number of special forces troops to help African militaries combat the brutal Lord's Resistance Army of Joseph Kony, Clinton will return to the security theme.
The tour also includes a private meeting with Nelson Mandela, now 94, in his hometown of Qunu.
Her last stop will be in Ghana, where she will attend the August 10 state funeral for the country's late president, John Atta Mills, who died last week.