The ICC's appeals chamber said it rejected a defense challenge to release Ntaganda, who surrendered to the court last year.
Ntaganda's defense team argued some of the evidence used by U.N. experts was based on hearsay, though the court ruled the methodology used to collection information was "quite rigorous," the ICC said Wednesday.
Two arrest warrants were issued by the ICC for Ntaganda, who is charged with multiple counts of war crimes and crimes against humanity as leader of a rebel campaign in the Democratic Republic of Congo from 2002 to 2003. His confirmation of charges hearing started last month to determine if there's enough evidence to go forward with a trial.
Marc Desalliers, defense counsel for Ntaganda, had said the warlord's militia was working to protect civilians when DRC authorities were absent.
DRC is struggling to restore national security after brokering an agreement with the rebel March 23 Movement, which waged war against the government from the country's eastern provinces. Human rights groups say M23 was one of more than a dozen armed groups fighting in the region.