He said there would be a formal announcement of the city's position in the coming week, probably on Friday.
Mayor Nutter has expressed concern about the human rights of all immigrants, regardless of their legal status.
In a directive he issued a year ago, he barred municipal employees on official business from inquiring about the immigration status of any person, including, but not limited to, victims, witnesses, arrestees, and detainees.
Gillison said Police Commissioner Charles H. Ramsey and District Attorney Seth Williams "agree with the mayor" that the ICE-PARS arrangement should be terminated.
His announcement, which followed an hour of public testimony from immigrants about their fears and mistrust of the police, drew chants of Si, se puede! - Yes, we can! - from a mostly Latino audience that also included members of the city's Asian communities and a contingent of suburban supporters from the Central Baptist Church of Wayne.
Organized by a coalition of proimmigrant groups, including Juntos and the New Sanctuary Movement, the standing-room-only meeting took place in the basement of Annunciation Church of the Blessed Virgin Mary on South 10th Street. It was conducted mostly in Spanish, with electronic headsets available to permit simultaneous translation into English.
In addition to Gillison, officials in attendance included City Councilwoman Maria Quiñones Sánchez; Police Capt. Michael Weaver, commander of the immigrant-rich Third District in South Philadelphia; and Leslie Davila, assistant director of Victims' Services, who represented the District Attorney's Office but who left before the end of the meeting without addressing the group.