Rebel leaders in Nigeria's Delta region have tentatively agreed to disarm, raising hopes of an end to fighting and attacks on oil installations.
Clashes between rebels and security forces have escalated
One leader, Moujahid Dokubo Asari, said the government had recognised that different groups had a right to partly control their natural resources.
But Mr Asari said he still opposed the presence of foreign firms in the area.
Uncertainty over Nigerian oil output helped push world oil prices to more than $50 a barrel on Friday.
Mr Asari had threatened "all out war" if demands for self-determination for the Ijaw people and a greater share of the country's oil wealth were not met.
"We've agreed tentatively to disarmament, but all the issues must be taken together, including the demands for self-determination and control of our resources," he told the AP news agency after talks with government officials.
Mr Asari is the leader of the Niger Delta People's Volunteer Force. Officials reject his claim to be fighting for self-determination and dismiss him as an oil thief.
But despite going into hiding in the Delta earlier this year, Mr Asari was invited to the capital Abuja for the latest talks.
The area has also seen seven years of ethnic fighting between Ijaw and Itsekiri militias.
A statement on Friday by the Nigerian presidency said Mr Asari had also agreed to disarm and disband his militia, but this has not been confirmed by the rebels.
"The groups affirm commitment to the peace offer by the
president, promise to cease all hostilities against themselves and
all economic and social interests of the Nigerian state," the statement, quoted by AFP news agency, said.
Asari has not confirmed he is disbanding his militia
Mr Asari had threatened foreign workers and said all foreign oil companies should cease all production by Friday.
In an Independence Day address on Friday, President Olusegun Obasanjo referred to the rebels as "rascally elements", but said a rapprochement was taking place.
The Nigerian president called on state officials to be more responsive to the plight of the people they were elected to govern.
Nigeria is the world's seventh largest exporter of oil, but 70% of the population live in poverty.
Mr Asari and his followers took to the creeks of River State earlier this year, and hundreds of people have died in subsequent clashes with the police, navy and rival gangs.
Fighting has intensified in the last month since the military launched a major operation against the group.
Last week, Shell pulled out more than 200 of its non-essential staff from two gas and oil fields because of heightened tensions.
Mr Asari has said negotiations with the government will resume on 8 October.