It might be the case right now but it came out earlier this year that the CIA was entertaining this idea in 2017. This [0] appears to be the originating story and there are corroborating accounts in many other outlets.
> Planning to commit a murder or a terrorist attack is a felony that will put an individual in prison for a long
Unless it is with other people and, more critically, at least one of the people involved goes beyond planning and takes some concrete step to advance the execution of the plan (at which point it becomes the separate crime of conspiracy), no, planning a crime, even of that seriousness, is not itself a crime.
CIA, DoD, and lots of agencies “entertain” lots of ideas, and even develop plans, for lots of things that never get close to being policy.