The United States has called on all sides in Nigeria including the military to ensure that next week's election is "free from outside pressure and intimidation."
Secretary of State Mike Pompeo in Washington said that February 16 vote offered "an opportunity for Nigeria to solidify its place as a democratic leader in Africa."
In a statement, Pompeo said, "The US government supports a free, fair, transparent and peaceful election that reflects the will of the Nigerian people,".
Fraud accusations and violence have marred elections since civilian rule was
restored in 1999 in Africa's most populous country. Although observers say the last vote in 2015 that elected were generally fair.
President Muhammadu Buhari is running for a second term against former vice president Atiku Abubakar, whose main opposition party has accused the ruling forces of trying to rig the vote.
The United States has built political and economic relations with Nigeria since the restoration of democracy and in recent years has been especially involved in supporting its fight against Boko Haram extremists.