Four men charged with plotting to kill Americans by aiding terrorists in Afghanistan have pleaded not guilty to a conspiracy count in a U.S. court.

A federal judge in Riverside, Calif., set an Aug. 6 trial date for the men after they made their first joint appearance in court Wednesday.

Three of the men — Ralph Deleon, Arifeen Gojail and Miguel Santana Vidriales — previously pleaded guilty. But they had to re-enter their pleas when prosecutors added to the indictment a Southern California man suspected of being the ringleader of the plot.

The government accuses Sohiel Omar Kabir of Pomona of inviting his co-defendants to visit his native Afghanistan and meet with terrorists. Gojali, Deleon and Santana were arrested the day they were suspected of leaving to meet Kabir in Afghanistan.

(AP)