Mend say they are campaigning for a greater share of the oil wealth
Ex-US President Jimmy Carter could play a positive role in mediating between Nigeria's government and oil militants, a Rivers State spokesman told the BBC.
Rivers is the last state where Movement for the Emancipation of the Niger Delta (Mend) militants are not in talks.
Militants have offered to stop attacks on oil production facilities if Mr Carter intervenes.
Attacks on oil installations in the delta have helped to drive up the price of oil.
Mend had issued a statement saying President Carter had "graciously accepted" an invitation to intervene.
The Carter Center denied this, but said Mr Carter would consider it if he was also invited by the federal government to do so.
"The Carter Center's correspondence with Mend emphasised that President Carter would seriously consider undertaking a mission if he were formally invited by all relevant stakeholders in the Niger Delta conflict," a statement from the Carter Center said.
A Nigerian government minister denied knowledge of any offer by Mr Carter, but promised to look into it.
Mend have claimed responsibility for attacks on oil installations this week.
A spokesman for the government of Rivers State in the Niger Delta, Ogbonna Nwuke, said Mr Carter could only be approached at a federal level, but his state would not have a problem if he became involved.
"But we cannot rule out the positive role that he may play through mediation," he told the BBC's Network Africa programme.
"We believe that the issues that are unfolding in the Niger Delta region are not as localised as many think; they have global dimensions," he said.
"Our concern is the best way forward in finding answers of underdevelopment in Niger Delta and unemployment."
Mend emerged in 2006. They kidnapped oil workers and emailed pictures to news desks bringing attention to the Niger Delta.
Mend say they are campaigning for a greater share of the oil wealth, but government says they are criminals motivated by the ransoms they receive from oil companies.