Sub-Saharan Africa is enjoying an unprecedented oil exploration and production boom that is expected to transform the region from a modest producer to a key supplier over the next decade.

US attention has focused on the Atlantic waters of the Gulf of Guinea states — Nigeria, Equatorial Guinea, Chad, Cameroon, Gabon, the Republic of Congo, Angola and São Tomé.

As head of a task force on future oil supplies, Dick Cheney, the US Vice-President, predicted two years ago that the region would become the fastest-growing source of energy for America. But the scale of the region’s untapped resources has taken everyone by surprise.

The US already imports about 15 per cent of its annual oil requirements from the Gulf of Guinea. This is expected to exceed 25 per cent by 2015, significantly reducing America’s dependence on the volatile Middle East.

US imports from Angola alone rose to $3.2 billion (£1.9 billion) in 2002, up from $2.3 billion in 1998. Angola produces 900,000 barrels of oil a day and is expected to exceed 1.6 million barrels a day at its peak. Some analysts predict that the Gulf of Guinea states are likely to earn about $200 billion while the boom lasts.

Foreign oil companies are pouring billions of dollars into new exploration and production projects, which will see oil extraction double. More than $50 billion has been earmarked for new development schemes, making it the single largest investment in the continent’s history. But there is mounting concern that America’s scramble for Africa’s resources will lead to an increase in the corruption and mismanagement that has afflicted the continent.

Catholic Relief Services (CRS), a Baltimore think-tank, has issed a blunt warning that the Bush Administration’s new-found interest in Africa is far from charitable.

In its report, Bottom of the Barrel, CRS said that petro- dollars had not helped developing countries in the past.

“Angola used them to fight a three-decade-long civil war, and in Nigeria they supported one military dictator after another,” Ian Gary, the report’s author, said.

CRS has been campaigning for greater transparency in the international oil industry in an effort to stamp out corruption and ensure that oil revenues are used to improve the lives of impoverished Africans, the bulk of whom live on less than $1 a day.

During his visit, Mr Bush is expected to emphasise American support for good governance and respect for human rights. But CRS doubts that such values will be allowed to get in the way of US strategic issues.

“The US has identified increasing African oil imports as an issue of national security and has used diplomacy to court African producers regardless of their record on transparency, democracy, or human rights,” Mr Gary said