A National Conference to discuss Nigeria's future is opening, with the division of oil money and powers expected to be the main issues.
Some 500 delegates are attending, representing Nigeria's many ethnic, linguistic and religious groups.
The National Conference comes 100 years after the mainly Muslim north and largely Christian south were united.
Delegates have been barred from discussing whether the country should be divided.
However, some groups say they will still raise this issue during the three-month conference in the capital Abuja.
Critics, including the main opposition party, have dismissed the conference as a waste of time and money.
The oil is located in southern Nigeria and some delegates from oil-producing areas want local communities to keep more of the revenue it generates.
However, poverty levels are far higher in the north and delegates from non-oil-producing areas are expected to resist such moves.
At present, oil states keep 25% of the oil revenue they earn and hand the rest to the federal government.
Nigeria is one of the world's biggest oil producers but most of its 170 million people live in poverty.
Some Nigerians want more powers to be delegated to the country's 36 states.
BBC Hausa editor Mansur Liman says it appears as though President Goodluck Jonathan wants to use the conference to change the constitution, which would otherwise be very difficult to achieve.
The conference comes ahead of elections next year, in which the governing People's Democratic Party is expected to face its strongest challenge since the end of military rule in 1999.
It also comes amid almost daily attacks by militants, suspected to be from Boko Haram, which wants to govern northern Nigeria according to Islamic law.
Despite its vast resources, Nigeria ranks among the most unequal countries in the world, according to the UN. The poverty in the north is in stark contrast to the more developed southern states. While in the oil-rich south-east, the residents of Delta and Akwa Ibom complain that all the wealth they generate flows up the pipeline to Abuja and Lagos.
Nigeria's 160 million people are divided between numerous ethno-linguistic groups and also along religious lines. Broadly, the Hausa-Fulani people based in the north are mostly Muslims. The Yorubas of the south-west are divided between Muslims and Christians, while the Igbos of the south-east and neighbouring groups are mostly Christian or animist. The Middle Belt is home to hundreds of groups with different beliefs, and around Jos there are frequent clashes between Hausa-speaking Muslims and Christian members of the Berom community.
Southern residents tend to have better access to healthcare, as reflected by the greater uptake of vaccines for polio, tuberculosis, tetanus and diphtheria. Some northern groups have in the past boycotted immunisation programmes, saying they are a Western plot to make Muslim women infertile. This led to a recurrence of polio, but the vaccinations have now resumed.
Female literacy is seen as the key to raising living standards for the next generation. For example, a newborn child is far likelier to survive if its mother is well-educated. In Nigeria we see a stark contrast between the mainly Muslim north and the Christian and animist south. In some northern states less than 5% of women can read and write, whereas in some Igbo areas more than 90% are literate.
Nigeria is Africa's biggest oil producer and among the biggest in the world but most of its people subsist on less than $2 a day. The oil is produced in the south-east and some militant groups there want to keep a greater share of the wealth which comes from under their feet. Attacks by militants on oil installations led to a sharp fall in Nigeria's output during the last decade. But in 2010, a government amnesty led thousands of fighters to lay down their weapons.