Two suburban Chicago men accused of seeking to provide material support to terrorists and who posed for photos holding an Islamic State group flag have pleaded not guilty to federal terrorism charges.

Joseph D. Jones and Edward Schimenti calmly told Judge Andrea Wood Wednesday that they understood the gravity of the allegations. The 35-year-olds from Zion face 20-year maximum prison terms if convicted.

A prosecutor at their arraignment in Chicago called it a complex case involving classified evidence that will remain sealed. The next hearing is July 6.

A complaint unsealed after their April arrests in an FBI sting says they agreed to provide cellphones that could be used as car-bomb detonators in Syria. It includes photos of them holding a black IS flag at Illinois Beach State Park.