Updated 5/31/12, 11:25 a.m. PT
The comedy is about two retired boxers who return to the ring for a final grudge match. While not yet green-lit, the movie is a "go" project at the studio expected to film early next year.
Peter Segal, whose credits include “Anger Management” and “Tommy Boy,” will direct.
Warner Bros. and De Niro's representatives declined to comment on the report. Stallone's representatives said he is considering the role.
There have been a few writers on the project, with "Entourage" creator Doug Ellin scripting the latest draft.
Mark Steven Johnson is producing, as are Gerber Pictures’ Bill Gerber and Carrie Gillogly. Johnson directed "Daredevil."
De Niro will have to fit this into a crowded schedule. He will appear in three more movies this year and has four more set for 2013 openings. Stallone will star in "The Expendables II," set for release later this year, and has a pair of projects on deck for 2013.