The personnel will support the operation of "intelligence, surveillance, and reconnaissance aircraft" for missions over northern Nigeria and the surrounding area, Xinhua quoted Obama as saying in a letter to Congress.
"The force will remain in Chad until its support in resolving the kidnapping situation is no longer required," Obama added.
Over 200 girls from Chibok community in northeastern Nigeria's Borno State were abducted in April. Extremists group Boko Haram claimed responsibility for the act in a video and threatened to sell the girls.
On May 12, a Pentagon spokesman, said that 16 military personnel from US Africa Command had joined the international effort to help find the kidnapped schoolgirls.