The United States says it is closely watching the situation in Nigeria's Niger Delta, where a local rebel group has threatened to shut down oil production. The State Department said the Nigerian government has a responsibility to keep the peace in the area.
The threat by the local rebel group, the Niger Delta People's Volunteer Force, has contributed to the sharp run-up in world oil prices this week.
And it is being viewed with concern in Washington, where the State Department said it is watching the situation in the delta very closely, and has warned Americans working in or traveling through the region to exercise caution.
At a news briefing, State Department spokesman Richard Boucher called the security situation in the area, Nigeria's source of low-sulphur crude oil for export, as unpredictable.
He said the United States has made clear to Nigerian authorities that they have a responsibility to keep the peace in the area, for the sake of its local population as well as the safety of American citizens and property.
Mr. Boucher said U.S. officials have been working with U.S. oil firms, Nigerian officials, and with non-governmental organizations to try to deal with the security situation in the delta as well as underlying problems of extreme poverty and poor governance.
"We have noted that although the states in this area receive more revenue from the government than in other parts of Nigeria, these states are among the poorest in the country. And so those problems are things that we recognize, and we've tried to work with American companies, with Nigerian authorities to try to rectify, to try to help the people of that area," said Mr. Boucher.
A senior diplomat who spoke to reporters here said the threat against the region's oil output appeared to be a renewal of tribal tensions in the Niger Delta that have flared into violence in the past.
The Niger Delta People's Volunteer Force, which says it fights for the interests of the ethnic Ijaw people, has said it would commence an all-out war against the Nigerian government starting Friday to gain more control over the region's oil wealth.
A Nigerian military spokesman has vowed to protect oil installations and dismissed the rebel warning as an empty threat.