New York City police have arrested an American-born Muslim in an alleged terror plot. Sketchy details are provided by the New York Post. The man, whose name has not yet been disclosed, is said to be in his 20s and to have schemed to attack at least one synagogue.

Oddly, it is said that the feds were not interested in the case, which was apparently pursued by the Manhattan district attorney’s office after the FBI declined to get involved. I say this is odd because the FBI and the NYPD work together in the Joint Terrorism Task Force, and most cases are taken federal. But the NYPD also has an intel/anti-terrorism capacity that is very robust, and the City acts independently of the feds from time-to-time, much to the dismay of the feds.

We will get more information later: A press conference is scheduled for later today. Mayor Bloomberg and Police Commissioner Ray Kelly will appear.

UPDATE: In a demonstration of what I describe above as the often tense relationship between the feds and the NYPD, the Post also reports that the inspector who was second-in-command for the NYPD on the Joint Terrorism Task Force has been relieved of his post and reassigned. His offense? He defied the order of his boss — the deputy police commissioner for intel, David Cohen — to bring Cohen the FBI’s latest dossier on Osama bin Laden. The inspector, John Nicholson, was caught in a no-win situation between the demand of his NYPD superior (who could easily have called his FBI counterpart and made the request personally) and the FBI’s policy of not allowing its sensitive files to be removed from its premises. Nicholson, whose background is naval intelligence, was transferred too oversee ordinary crime patrol cops in Brooklyn. I’d love to be able to tell you that this sort of petty stuff is unusual, but . . .