Italy's national news agency Ansa claim the Serie A leaders have agreed terms with the Genoa outfit for the permanent transfer of Cassano to the San Siro.
The 28-year-old striker is expected to sign a contract with Milan on Tuesday.
The Rossoneri confirmed last week they were in negotiations with Samp to acquire the Italy international.
Milan, Samp and the player will contribute in equal parts towards the five million euros fee that the Genoa club are supposed to pay Real Madrid - Cassano's former club - should the transfer take place.
The troubled striker has not featured for Samp since being dropped from the squad back in October following a heated argument with club president Riccardo Garrone.
Samp attempted to rescind the player's contract but were unsuccessful.
However, Cassano was punished last week by an arbitration panel with his wages reduced by 50% for the duration of his contract with Samp, which expires in June 2013.
Moreover, he is suspended until January 31st, 2011.
