They had previously been charged with conspiracy to commit such an attack. That conspiracy charge remains against all five men.
The superseding indictment does not spell out why the attempt charge was added.
U.S. Attorney's Office spokesman Greg Reinert declined to elaborate.
Rocco Cipparone Jr., lawyer for Mohamad Ibrahim Shnewer, says the charges were anticipated.
Michael Huff, lawyer for Dritan Duka, said, "If your client is innocent of the charges, it doesn't matter what he is charged with."
