Nigeria has refused to issue an entrance visa to former U.S. Ambassador to Nigeria John Campbell, saying he did not meet visa requirements.
The visa was denied in Washington, D.C. after Campbell raised concerns about Nigeria's political stability.
Campbell has written extensively on Nigeria's stability. Recently he has expressed doubts that Nigeria can continue to exist as a nation after the 2011 elections. He has called the 2011 elections a threat to the stability of America's most important partner in that region.
He has expressed concerns that members of an extremist Muslim sect in the nation's northeast might form an alliance with al Qaeda.
Campbell reportedly requested a visa to attend a graduation ceremony at Abti University, Yola. The university is owned by former vice president Atiku Abubakar, who mounted a failed presidential bid earlier this year.
Campbell served as U.S. ambassador to Nigeria under former President George W. Bush from May 20, 2004, to Nov. 1, 2007. He is currently a fellow at the Council on Foreign Relations in New York.