Milan chief executive Adriano Galliani confirmed the possible exchange between the rival clubs after the Rossoneri's 3-2 defeat by Serie A champions Juventus in the Berlusconi Trophy friendly on Sunday.
"Talks are ongoing. Antonio has asked to be sold, let's see what happens. The most probable scenario is a swap," he told reporters.
The deal would seem to make sense for both sides who are not immune to doing business together and saw rivals Juve seal the scudetto last term after the Milan duo had dominated for five years.
Milan and owner Silvio Berlusconi are cutting costs and sold top striker and former Inter player Zlatan Ibrahimovic to Paris Saint-Germain last month but have so far failed to replace the powerful Swede, angering fans who feel the club have lost ambition.
Italian international Cassano, who has only been at Milan for a year and a half and was struck down by a heart complaint for much of last term, said at Euro 2012 in June that he was unsure about his Rossoneri future.
Milan need an out-and-out striker like Pazzini to replace Ibrahimovic. Cassano plays more in the 'hole' behind a forward and Massimiliano Allegri's side already use Robinho in that role.
Inter and Pazzini struggled in front of goal last term and the Italy striker, who missed out on being picked for Euro 2012 where the Azzurri lost to Spain in the final, has long been linked with a move.
A transfer to seven-times European champions Milan is better than the 28-year-old could have ever hoped for as he tries to reignite his career.
The Serie A season starts this weekend with a cloud over Juve after manager Antonio Conte was banned for 10 months for not reporting match-fixing while at Siena. He is appealing against the suspension.
