Nigeria�s president and vice- president have called for each other�s resignation in what is seen by diplomats as a significant threat to stability in the world�s eighth largest oil exporter.
A statement from the office of Atiku Abubakar, Nigeria�s vice-president, said on Thursday that President Olusegun Obasanjo should resign for pursuing an attempt to amend the constitution and stay in power for a third term.
The president�s office had earlier called for Mr Abubakar to resign after he attended a high-profile meeting this week of legislators and political figures in the capital Abuja opposed to a third term.
The third term has become a national obsession as Nigeria heads towards national elections next year, when Mr Obasanjo is constitutionally due to step down. He has not been forthcoming about whether he will run for a third term, although his allies have been pushing for constitutional change.
Supporters of Mr Obasanjo and the vice-president be-lieve that neither will resign, although the deterioration in relations signifies a further breakdown in governance.
Tensions are high among the political elite, who expect a geo-political reordering if and when Mr Obasanjo, a Christian southerner, steps down. Politicians from the Muslim-dominated north expect to see a Muslim northerner as the next president.
The tensions manifested themselves earlier this year in a bout of religious violence, which killed at least 130 people. The oil-producing Niger Delta has also been subject to militant attacks that have cut about a quarter of the oil output.
Speculation that Mr Obasanjo may stay on has alarmed some western governments, which fear a backlash against the president, who came to power as a consensus candidate after the end of 15 years of military rule in 1999. Relations between him and Mr Abubakar have been strained for many years.
John Negroponte, US intelligence chief, said this year that a third-term attempt by Mr Obasanjo could unleash �major turmoil and conflict� in Nigeria and the region and could lead to large disruptions in oil supply.
Legislators said Mr Obasanjo did not have the two-thirds majority in the national assembly to change the constitution, with both chambers evenly split.
Mr Obasanjo earned democratic credentials when, as a military ruler, he handed back power to a civilian government in 1979.
Since returning to power he has tried to reform Nigeria�s opaque institutions but has met resistance in many areas. His critics say he has used his anti-corruption agency to wield power and resorted to authoritarian means to repress dissent.