Brad Pitt and Denzel Washington have entered early talks to star in the Lionsgate movie, according to The Hollywood Reporter.
The 'two-hander' crime thriller centres around a former deep-cover operative who settles down to the quieter life of a Brooklyn beat cop.
He soon discovers that trouble has followed him in the form of a global crime organisation he previously tackled who have set up shop in his neighbourhood.
Jamie Foxx is also reported to have shown interest in one of the roles.
Gaghan directed 2005's Syriana and won an Oscar for his writing work on the Steven Soderbergh-directed Traffic in 2000.
Pitt will be seen in Ridley Scott's forthcoming drama The Counselor.
Washington's upcoming Flight will close the New York Film Festival.