Washington cut military assistance to Rwanda citing allegations the government was backing militants in the Democratic Republic of Congo that carried out a mutiny this year.
Stephen Rapp, director of the U.S. Office of Global Criminal Justice, told The Guardian newspaper in London that Rwandan authorities, including President Paul Kagame, could face charges of "aiding and abetting" in crimes against humanity in DRC.
Rwandan leaders had denied earlier allegations. Fighters loyal to rebel Gen. Bosco Ntaganda mutinied in April, saying the government reneged on a peace deal that saw their forces integrated into the national military.
The BBC reported rebel forces, dubbed M23, are under assault north of the city of Goma. Civilians are reportedly fleeing the area as fighting is said to be taking place on multiple fronts.
M23 rebels and DRC forces were locked in battle in mid July.
Ntaganda is the subject of two arrest warrants issued by the International Criminal Court for crimes against humanity, including the conscription of child soldiers.
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