"My intentions are to try to go back after next year and force my way into the All Blacks squad."
who is also New Zealand's heavyweight boxing champion,
won the National Rugby League (NRL) with the Roosters last season and says the chance to help them become the first side since Brisbane in 1993 to successfully defend the title persuaded him to delay his departure from the 13-man code.
"A major factor in my desire to play next year was to try to go back to back, because it hasn't been done for so long," he added.
"I know it will be hard for me to force my way back into the New Zealand rugby [union] set-up, but [another season in NRL] was just something I felt was right and I just went with my heart in the end.
"I decided that I wanted to stay with the boys because it is tough leaving when you are a part of the start of a successful thing.''
Although New Zealand Rugby general manager Neil Sorensen had described Williams' decision to turn down their three-year offer as "disappointing", All Blacks coach Steve Hansen admitted the centre would be "very hard to leave out" of his side's world title defence in England in September 2015.
Archive - Highlights of Williams' debut against England (Nov 2010)
A stint in Japanese club rugby preceded his return to league for the 2013 NRL season with the Roosters. This month he was
a late addition to the Kiwi squad
for their Rugby League World Cup defence in England and Wales, having initially said he was unavailable.
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