The United States has condemned the abduction of more than 200 Nigerian schoolgirls by Islamist militants as an "outrage".
White House spokesman Jay Carney told reporters on Monday that President Obama had been briefed several times on the matter.
He said that the US State Department had offered its assistance to the Nigerian government to help recover the girls.
The comments followed the release of a video of the leader of the Islamist group Boko Haram, saying it had abducted the girls and intended to sell them.
