The Brazilian forward has been in talks with Corinthians and has apparently made up his mind over the permanent transfer.
No details have been revealed regarding a fee but his agent claims an agreement is in place with AC Milan and all that is left to do is conclude the details of Pato's contract.
His representative, Gilmar Veloz, told Radio Gaucha: "We have a meeting with (Milan's vice-president) Adriano Galliani this Wednesday and we plan to take the final step. It's very close. Corinthians have accepted all Milan's demands."
Veloz added: "I believe that within two days, things will be done. It's a permanent signing. Nobody loans out 23-year-old players. Pato had other offers but decided to return to Brazil."