Boca intend to takeover Osvaldo's loan from Inter Milan and hold onto him for the next six months. Saints have agreed to cover a small percentage of the striker's existing salary.
The deal will include a permanent option in June.
Boca vice-president Marcelo London told Calciomercato.com: "We are waiting for Osvaldo.
"We are convinced that the operation can be done, we will see what he will decide but these are decisive hours."