President Barack Obama said the US has deployed around 80 military personnel to Chad as part of its effort to help find and return more than 200 Nigerian schoolgirls kidnapped by Islamist militant group Boko Haram.
In a letter to Congress on Wednesday, Obama said: "These personnel will support the operation of intelligence, surveillance, and reconnaissance aircraft for missions over northern Nigeria and the surrounding area.
"The force will remain in Chad until its support in resolving the kidnapping situation is no longer required.
The Nigerian military has flown more than 300 sorties in the hunt for the abducted schoolgirls, a Major has told ITV News' Rageh Omaar.
A newly released video from Boko Haram reportedly shows the kidnapped Nigerian schoolgirls.
The man who started a viral hashtag campaign in support of the kidnapped Nigerian schoolgirls says it has forced the government to act.