The 28-year-old former All Black, who made a spectacular return to league with newly crowned NRL champions Sydney Roosters this year, was on Monday left out of the Kiwis' 24-man squad, apparently confirming rumours of an imminent return to the 15-man code.
The New Zealand league cited "other commitments" as the explanation for Williams' absence but, according to the Sydney Morning Herald, the second rower has undergone a change of heart and advised national coach Stephen Kearney that he is keen to end a six-year absence from the Kiwis team.
"I've seen the report and we're still working our way through it," New Zealand's media manager Caley Wilson told Press Association Sport.
"I'm getting a mountain of calls on the subject but I can't shed any light at the moment.
"Stephen is on his way back to Brisbane after the press conference in Auckland. I dropped him off at the airport this afternoon and he's spent most of the later part of the day in the air.
"He spoke to Sonny Bill yesterday but whether he's had another conversation I'm not sure yet."
If the report is true, the presence of one of the game's leading players would provide a major boost to New Zealand's title defence - and the tournament itself which gets under way in Cardiff on October 26.
Williams helped the All Blacks win the World Cup in 2011 but has has yet to win with the Kiwis, having lost six and drawn one of his seven Tests so far.
The dilemma for Kearney would be how to accommodate the player in his 24-man squad, which once submitted can in theory only be changed in the event of injuries.