She met top leaders and oil executives as she called for closer cooperation in the energy sector in the former Cold War adversary, which is the biggest oil supplier to China and has seen a surge in Chinese influence.
But while China has largely shied away from human rights issues, Clinton addressed them in a televised news conference, calling for President Jose Eduardo Dos Santos -- who has ruled Angola virtually since independence from Portugal in 1975 -- to hold presidential elections.
Clinton said she was "encouraged" that Angola held "peaceful and credible" legislative elections last year, the first in 16 years. The vote followed the end of a devastating 27-year civil war in 2002.
"We look forward to Angola building on this positive step by including adopting of a new constitution, investigating and prosecuting past human rights abuses and holding timely, free and fair elections," Clinton said.
Dos Santos, whom Clinton will meet on Monday, has indicated that he will delay landmark presidential elections due this year, saying that work still needs to be done on drawing up a new constitution.
Clinton also called on Angola to do more to spread oil wealth to its poorest citizens and said that prosperity for ordinary people "depends on good governance and the strengthening of democratic institutions."
Angolan Foreign Minister Assuncao Dos Anjos, speaking at the joint news conference with Clinton, outlined efforts to reduce poverty but also defended delays.
"We've been criticised because we didn't have elections.. (but) we asked for more time and we did it," he said in the manicured garden of the pink Portuguese-inspired presidential palace.
"We're asking for more time now," he said of development. "We have the structure, we have the willingness and we can ensure better lives for our people. But there's no magic wand."
Clinton said she was not concerned that China may seize on resentment to perceived US hectoring to gain advantage in Angola's oil sector, which accounts for two-thirds of the nation's revenue.
"I'm not looking at what anyone else does in Angola," she said.
"I'm looking at what the United States can do to further and deepen our relationship and provide assistance and support for the changes the Angolan government is undertaking."
Clinton also met with Angola's opposition UNITA -- former US-backed rebels who battled Dos Santos' Soviet-allied government in the civil war.
Alda Sachiambo, the parliamentary leader of UNITA, asked Clinton to pressure Dos Santos to curb alleged abuses, including what she called "institutionalised corruption."
"We don't need strong men, we need strong institutions," she told Clinton.
Yet there was little tension in the visit. Angola rolled out half its cabinet for meetings with Clinton, whose trip was covered live on television from the moment her plane touched down in the bustling capital Luanda.
A senior US official, speaking on condition of anonymity, said Clinton cast her message as working with Angola rather than lecturing.
"We feel Angola is moving in the right direction, so her message was that we encourage you to keep up the momentum," the official said.
Clinton called for Angola to play a wider role in Africa and discussed starting a Peace Corps mission in the country, the official said.
Angola is the third stop on Clinton's Africa trip in which she has made good governance a major theme. On her first stop, she pressed rival leaders in Kenya to move ahead on democratic reforms.
She heads Monday to the Democratic Republic of Congo.
The focus on energy security was unusual for Clinton, who has made the fight against climate change a signature policy. Clinton said that she also spoke to Angola about how to reduce greenhouse gas emissions.
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