The 32-year-old Williams' playing future has been the subject of intense speculation virtually every year since he walked out on a five-year contract with rugby league's Canterbury Bulldogs in 2008 to play union in France.
Williams was forced into clarifying his future after a former Sydney Roosters player told an Australian radio station at the weekend that he would join the club in August after the Auckland Blues' season ended.
"I love being a part of the Blues Rugby team & All Blacks," Williams wrote on his Twitter account on Monday.
"God willing I'm a part of another successful World Cup Campaign next year in 2019."
Williams, who played for the Roosters in 2013-2014, is contracted with the Blues and New Zealand Rugby until after the 2019 World Cup.
New Zealand media treated the report with derision on Monday, while a NZR spokesperson told the New Zealand Herald they did not want to give "oxygen to a story that was patently wrong".
The Roosters also denied the story.
Williams has won two Rugby World Cups with the All Blacks but missed the 2016 season as he committed to playing rugby sevens at the Rio Olympics.
He ruptured his Achilles' tendon at Rio and made a slow return to form last year with 15s, but was arguably among the most consistent of players in the side by the end of the year and was an automatic selection.
Williams was also promoted to the All Blacks' leadership group last year.