Nigeria's president Muhammadu Buhari has invited the United Nations to help negotiations to swap the kidnapped schoolgirls from Chibok for detained leaders of Boko Haram, a government statement said.
Mr Buhari's government has been criticised for failing to free the Chibok girls by parents of the abducted students, community leaders and human rights activists.
Boko Haram has kidnapped thousands of people but the mass abduction of 276 schoolgirls in April 2014 incited outrage around the world and brought international condemnation of Nigeria's home-grown Islamic extremist group.
Dozens of the girls escaped on their own within hours, but 217 remain missing.
Mr Buhari's request for UN intermediaries is a "show of commitment" made to secretary general Ban Ki-moon on Wednesday on the sidelines of the UN General Assembly in New York, said a statement from presidential adviser Femi Adesina.
Mr Buhari told Mr Ban that his government is "willing to bend over backwards" to win the girls' freedom but finding credible Boko Haram leaders for the negotiations has been difficult, especially because of the current leadership struggle among the militants.
Longtime Boko Haram leader Abubakar Shekau's faction in August posted a video showing about 50 Chibok girls and offering a prisoner swap.
An unidentified fighter in the video suggests the government deal with a journalist trusted by the militants. That was an apparent reference to Dubai-based Nigerian journalist Ahmad Salkida, who was subsequently detained by Nigerian intelligence agents, and then released.
He was accused of knowing the whereabouts of the girls - which he denied.
Last week, information minister Lai Mohammed said the government had nearly secured the girls' release three times but negotiations collapsed.
Most girls kidnapped by Boko Haram have been forced to marry fighters and are pregnant or have babies, according to some of the thousands freed in the past year as the military has recaptured territory.