ARL Commission chief executive Shane Mattiske also doused fears Williams's NRL contract had not yet been ratified, rejecting the idea Williams could renege on an NRL deal as AFL convert Israel Folau had done.

New Zealand assistant coach Tony Iro said the Kiwis had not officially spoken to Williams about his availability for Test match football; Williams rejoins the NRL with the Roosters in 2013.

Williams won't be included in a 35-man Kiwi squad that will assemble for a camp in January, but Iro said the rugby union convert was ''definitely in our plans''.

Williams, who is recovering from a pectoral injury, will have up to six NRL matches to prove he is ready for a return to international rugby league before the Anzac Test against Australia at Canberra Stadium on April 19.

''We're really excited about him coming back into the game,'' Iro said. ''Once he gets settled back into the NRL then we can establish whether he's ready. But he's definitely in our plans.

''We've left Sonny alone at the moment, he's got an injury he needs to get fixed first. What I do know is that Sonny is a proud Kiwi so I'd imagine that if he's 100 per cent physically and mentally, he'll be ready to go.

''If he plays to his potential he's probably going to get picked.''

The Kiwis are aiming to defend their World Cup title at the end of next year and Australian coach Tim Sheens said the return of Williams would boost New Zealand's chances.

The Kiwis have not won a mid-year Test since 1998, but Sheens conceded a fully fit Williams made New Zealand much more formidable.

''If he's available for that Test match [in Canberra] it's only to give them that extra edge in confidence too, which sometimes the Kiwis lack a little of,'' Sheens said.

''So a player of his calibre and ability is only going to improve that aspect of their game. We're going to be tested big time in April.

''It's really going to be four or five games to see how he goes, but the athlete he is and the memories he has of the game, I don't think that's going to be a big problem.

''It's just going to be the physicality and the speed is going to test him, I think.''

Rugby union World Cup winner Williams, who is yet to have his contract with the Roosters ratified by the NRL, is set to box against South African Francois Botha in Brisbane in February. He has already had five heavyweight fights and has a perfect winning record.

Mattiske rejected claims the NRL risked losing Williams to a rival sport if the league continued to stall on his contract.

Rugby union recently snuck under the nose of the NRL to snare Folau when there were issues and delays in the AFL convert signing a contract with the Parramatta Eels.

''With Sonny Bill a signed contract has been presented to the NRL for registration so it's a very different situation to Israel and we're simply working through the process at the moment of registering his contract,'' Mattiske said.

''He's actually signed a contract with the Roosters.''