The formalities of the agreement are expected to be completed when the transfer window opens on January 1.
Sorsa will be available on a free once his contract with Finnish club HJK Helsinki expires on New Year's Eve.
The winger has represented Finland at u-21 level, and has also featured for HJK Helsinki in the UEFA Cup.
Wise said: "We've spoken with him, he's a free transfer and won't cost anything. He caught our eye and did very well so we're looking to bring him in. He plays on the wing and he's quick with a lot of ability as well. He's going to give a bit of competition."