The 28-year-old backrower, regarded by some as the best player in either rugby code, was a Rugby World Cup winner with the All Blacks before making his return to league this year with the Sydney Roosters.
Williams has yet to announce his plans for 2014 as he contemplates another stint in the 15-man game and the next stage of his boxing career, but he is a prime target for Kiwis head coach Stephen Kearney, whose side will be defending their World Cup trophy in the United Kingdom and France in October and November.
New Zealand team manager Tony Iro, who is in England checking on hotels and training facilities, says the Kiwis remain hopeful of having Williams on board.
"We're in conversation with him," Iro said. "He needs to make a decision on his next career move and we're waiting on that.
"We're obviously very keen to have him available... He would be fantastic, not only for New Zealand but for the World Cup.
"He's had a massive influence on the Sydney Roosters and I'm sure he would have a similar impact on the Kiwis."
Iro is less optimistic over the prospects of former captain Benji Marshall appearing in this year's tournament.
The Wests Tigers five-eighth, who was removed as Kiwis skipper earlier this year, is in wretched form for his club and will switch codes at the end of the year with Auckland Blues.
"He's still in our thoughts but I think it's unlikely he'll be available given that he's signed a rugby union deal," Iro said.
"His new employers by all accounts are not that keen on him travelling and the other consideration is that he's not been in great form."
Iro said they were under no illusions about how tough it will be to defend the trophy.
"I've not been sent (to London) by Stephen Kearney to talk down our chances but Australia have been the benchmark for a long time," he said.
"We happened to get a couple of tournaments off them but they are the team to beat, although I'm sure England as well as ourselves will make it tough for them."
