WASHINGTON, May 21 (Xinhua) -- The United States has deployed about 80 military personnel to Chad as part of its efforts to find more than 200 schoolgirls who have been kidnapped in Nigeria, U.S. President Barack Obama said Wednesday.

The personnel will support the operation of "intelligence, surveillance, and reconnaissance aircraft" for missions over northern Nigeria and the surrounding area, Obama said 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.

More than 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, Steve Warren, the Pentagon spokesman, said that 16 military personnel from U.S. Africa Command had joined the international effort to help find the kidnapped schoolgirls.

The group of 16 military personnel, including experts in communications, logistics, civil affairs, operations and intelligence, are among members of an interdisciplinary team led by the State Department at the U.S. Embassy in Abuja, capital of Nigeria, Warren told a press conference.