US Secretary of State Hillary Clinton said Nigeria's future is "limitless" - if the country's anti-corruption reform efforts continue.
She made the comments after meeting Nigeria's President Goodluck Jonathan in the Nigerian capital, Abuja.
Nigeria is one of the world's biggest oil producers, but has been plagued by corruption, she noted.
The closed-door talks also focused on the growing insecurity caused by Islamist militants.
Correspondents say there is a link between the stealing of oil money, widespread poverty and the current insecurity.
Nigeria, the US's fifth largest supplier of oil, has been plagued by allegations that its wealth has been used for corrupt purposes since the oil boom of the 1970s.
Mrs Clinton, who is touring Africa, said the US was very supportive of the Nigerian government's anti-corruption reform efforts.
"But the most important task that you face, as you have said, is making sure that there are better opportunities for all Nigerians - north, south, east, west - every young boy and girl to have a chance to fulfil his or her God-given potential," she said at press conference with Mr Jonathan.
In the US, politicians have been debating to what extent Boko Haram poses a danger to the US.