RNZ reports Gallen's resumed training in his stop-start boxing career ahead of two scheduled bouts in December.
Dual international, Roosters premiership winner and two-time Rugby World Cup winner Williams is in Gallen's sights.
But Williams is currently out of action for another six months after injuring his Achilles playing sevens rugby at the Rio Olympics.
"I have said openly I want to fight Sonny Bill, unfortunately we haven't heard the same thing back so I don't know if he wants to," Gallen said.
