The muscular New Zealand centre had signed a lucrative deal to play with Panasonic Wild Knights in Japan's Top League and was also poised to announce a deal with the Sydney Roosters in Australia's top-flight National Rugby League, Sydney's Daily Telegraph newspaper said.
The New Zealand Rugby Union , who coaxed Williams home from Europe in 2010 with the lure of an All Blacks jersey for the World Cup, declined to comment on the report, but said they had scheduled a news conference in Hamilton on Monday with the 26-year-old and All Blacks assistant coach Ian Foster.
Williams, 26, played one season with the Canterbury-based Crusaders in the southern hemisphere Super Rugby competition last year before crossing to the Chiefs this season.
Chiefs coaches Dave Rennie and Wayne Smith would also appear at the news conference, the NZRU said.
Dual international Williams began his professional career playing rugby league for the Sydney-based Canterbury Bulldogs in the NRL but controversially walked out on the team mid-season in 2008 to play rugby union with French club Toulon.