The US team, working with the Nigerian government, would do everything possible to free the girls, US Secretary of State John Kerry added.
As Nigeria has been criticised for its slow response to the kidnappings, the country’s President, Goodluck Jonathan, said he hoped “a turning point” had been reached in the fight against Islamist insurgents Boko Haram.
The schoolgirls were seized from their boarding school April 14 at night in the town of Chibok in north-eastern Borno state.
In a video released earlier this week, Boko Haram leader Abubakar Shekau threatened to “sell” the students as he said they should not have been in school in the first place and instead get married.
Speaking at the World Economic Forum being hosted in the capital Abuja, President Jonathan said the abduction of the girls could be a turning point in the battle against Boko Haram.
“I believe that the kidnap of these girls will be the beginning of the end of terror in Nigeria,” he said.