Paul Gallen has indicated he is set to fight former NRL rival Sonny Bill Williams in 2020, provided the prize money is evenly split.

After featuring for New Zealand at the Rugby World Cup in Japan, Williams has made headlines this week, switching back to rugby league to sign a two-year contract with newly promoted Super League club Toronto Wolfpack.

The 34-year-old's deal will reportedly make him the highest-paid rugby league player in the world, though it has now been reported a clause in his Toronto contract will allow Williams to fight Gallen in a heavyweight bout next year.

Sydney's Daily Telegraph newspaper report the fight will take place next October, with the two-time Rugby World Cup winner having initially agreed to face Gallen, who retired from the NRL at the end of last season, in 2017, only for the fight to be cancelled.

Gallen, 38, is taking on former AFL player Barry Hall in a heavyweight bout on Friday.

"I've got to deal with Barry Hall first and get him out of the way... we'll worry about Sonny later," Gallen told the Daily Telegraph.

"It will be a 50-50 split or it won't be happening. Everything was lopsided his way last time. Not anymore. I bring as much to the fight as he does.

"He'll make his couple of million so there will be no excuses for him to back away again."

Williams' agent, Khoder Nasser, shot down Gallen's claims.

"If Gal honestly thinks he's entitled to a 50-50 cut, the poor bugger has had too many head knocks," Nasser told the Telegraph.

Williams holds a 7-0 record as a professional boxer and beat veteran South African Frans Botha - who had previously fought the likes of Lennox Lewis and Wladimir Klitschko - by unanimous decision in 2013 to take the WBA International Heavyweight belt.