The US has “aided and abetted” the Boko Haram Islamist militant group by refusing to provide weapons to Nigeria, President Muhammadu Buhari says.
A US law prevents the government from selling arms to countries which fail to tackle human rights abuses.
Mr Buhari met President Barack Obama in Washington on Monday to seek further assistance.
Boko Haram has killed some 10,000 people since 2009 and has also kidnapped hundreds of girls and women.
Last month, human rights group Amnesty International said that some 8,000 men and boys had died in Nigerian military custody after being detained as suspected militants.
The military rejected this allegation, Nigeria’s president promised an investigation but there have been no further details.