"The Gulf of Guinea is a nexus of vital US foreign policy priorities," says the report from the Centre for Strategic and International Studies, noting that the region already supplies 15 percent of US oil imports, which is expected to increase to 25 percent by 2015 as more offshore fields come on line.

But while prospects for further oil exploration are good - over the next five years production is expected to increase by two to three million barrels per day - the corruption and instability of regional governments and the rise of well-armed criminal cartels and mercenary gangs menaces US interests.

'US energy security'

"In the short-term, a sudden violent disruption in the Gulf of Guinea will strain but not break US energy security or other major US interests. Less clear is how long the United States could comfortably withstand a severe and sustained interruption of oil and gas supplies," according to the authors.

Armed gangs and cartels could
threaten US interests

The report was prepared by the CSIS "Taskforce of Gulf of Guinea Security", which comprises oil executives, academics, diplomats and retired naval officers under the chairmanship of Nebraska's senator Chuck Hagel and received briefings from serving US ambassadors, oil companies, the CIA and US military commanders.

It recommends that the US government set up a fund to boost efforts to strengthen the governments in the region - particularly Nigeria, which holds 70 percent of estimated oil reserves and which is seen as particularly corrupt and unstable - and increase military cooperation with local navies and massively boost the US diplomatic presence around the Gulf of Guinea area.

Nigerian production has been severely disrupted by armed gangs in the Niger Delta over the past three years while smaller oil states Sao Tome and Equatorial Guinea have faced coup attempts backed by foreign adventurers.

Call for intervention

Failure to intervene more directly now could cost the US dearly.

"Sustained interruptions would increase US oil dependence on the Middle East, threaten the viability of US investment in the Gulf of Guinea and possibly American lives and draw the United States into increasing involvement in crime control, peacekeeping and other security programs," the report said.

Nigeria, Angola and Equatorial Guinea are major oil producers while Chad, Sao Tome, Cameroon and Congo are expanding their production.

There is no permanent US military presence in the region, although US forces help train local armies and last year US warships passed through the gulf in a "show of force".