US assistance to Nigeria focuses on information-sharing and improving Nigeria's forensics and investigative capacity, Xinhua quoted White House spokesperson Jay Carney as saying at a press briefing.
He added that "we view what has happened there as an outrage and a terrible tragedy".
Carney said President Barack Obama has been briefed several times on the issue and his national security team is monitoring the situation closely.
More than 200 girls from Chibok community in northeastern Nigeria's Borno State were abducted in April. On Monday, militant group Boko Haram claimed responsibility for the act and threatened to sell the girls.
"Boko Haram is a terrorist organisation with heinous and malicious intent," Carney said.
At a press briefing on Monday, State Department spokesperson Marie Harf said according to US information, many of the girls have likely been moved out of the country to neighbouring countries.
In November, US blacklisted Boko Haram as a terrorist organisation and slapped sanctions on it, including denied access to US financial institutions, a freezing on its assets in US banks and a ban on doing business with or providing support to it.