Her visits to Angola and Nigeria underscore the increasing importance the U.S. attaches to African oil as it seeks to reduce its need for Mideast oil. Clinton on Monday was wrapping up a two-day visit to Angola - which supplies vast amounts of petroleum and liquid natural gas to the U.S. market - and plans to go to Nigeria later this week on her seven-nation tour.
Clinton stressed the need for greater accountability and transparency, and urged the government of President Jose Eduardo dos Santos, in power in the former Portuguese colony since 1979, to adopt a new constitution, investigate and prosecute human rights abuses, and hold promised presidential elections.
Dos Santos "was very positive in his reaction to the points we were making," she told reporters traveling with her.
In 2008, the U.S. imported 1.05 million barrels of oil a day from Nigeria - almost as much as it bought from Saudi Arabia, making the West African country its fifth biggest oil source.
Angola to the south, was sixth at 468,000 barrels. For the month of June, Angola edged out Nigeria to become Africa's biggest producer. Nigeria's production has been slowed as militants attack its energy infrastructure.
Big oil revenues are a curse instead of a blessing to ordinary Nigerians and Angolans. Analysts note that petrodollars allow their leaders to ignore foreign critics, unlike other states on Clinton's itinerary that rely on foreign tourism, aid or peacekeepers.
The two nations are nominally democratic, but politicians feel little need to court voters.
Nigeria has a history of coups and the last elections here were marred by voting irregularities and police firing tear gas at lines of voters. In Angola's last parliamentary election, money, alcohol and even cars were dished out and many polling stations didn't open for lack of materials, international observers found. Angola was in civil war from the 1970s to 2002. It has not held presidential elections since the war ended.
Just last week, Global Witness, a London-based watchdog group, reported that several shareholders of a private firm authorized by Angola's state oil company to bid for lucrative contracts have the same names as top current and former Angolan officials, including the state oil company chairman. The officials have not responded to repeated requests from Global Witness and reporters for a response.
"Despite the widespread perception that government corruption at all levels was endemic, there were no public investigations or prosecutions of government officials during the year," said a report this year by the U.S. State Department.
More than two-thirds of 12 million Angolans and more than four-fifths of 150 million Nigerians live on less than $2 a day. Many feel neglected by their leaders.
"They don't care about the small man. Not at all," said Sam Olufemi, selling phone cards amid one of Lagos' perennial traffic jams. "It's pay-as-you-go politics."
Angola has suffered unrest in Cabinda, the main oil-producing region. Human rights groups have accused the military of atrocities and claim government officials have embezzled millions of dollars in oil revenue. The government has denied the charges.
Thousands have been killed over the years in Nigeria's oil-rich Delta, where the military battles criminal gangs by firing into slums from helicopter gunships and militant groups bomb pipelines and kidnap foreigners.
Diarmid O'Sullivan of Global Witness said one way the U.S. Congress could help is by passing the Extractive Industries Transparency Disclosure Act, which would require oil, gas, and mining companies listed on U.S. exchanges to publicly disclose their payments to the governments of countries whose riches they extract.
The bill was introduced in Congress last year but didn't pass. Campaigners are hoping it will be reintroduced this year.
--- AP writer Matthew Lee contributed to this report from Luanda, Angola.
