All Blacks midfielder Sonny Bill Williams will return to the NRL in 2013 after a stint playing Japanese club rugby.

The 26-year-old dual international told reporters in Hamilton on Monday he would play rugby league in 2013 but refused to elaborate on who he will be playing for.

Williams, who is believed to be joining Sydney Roosters next year, says he had a “handshake agreement” in place for the 2013 NRL season but nothing had been signed.

He will join the Panasonic Wild Knights in Japan later this year and will not return to New Zealand rugby after his five-month stint is over.

Japan’s Top League season begins on August 31, running until the end of January, and it has been estimated he will earn as much as $1.7 million for his time in Japan.

The timing of the Japanese season will allow Williams to make a return to rugby league in 2013.

Williams controversially walked out on his NRL team the Canterbury Bulldogs in 2008, just 18 months into a five-year deal to join French rugby club Toulon.

He was part of last year’s Rugby World Cup-winning All Blacks team, and showed commanding form in the three-Test series against Ireland last month.

Williams, who is nearing the end of a one-year deal with Super Rugby franchise the Chiefs, is also expected to continue his professional boxing career.