Sonny Bill's heart in rugby... league... and Olympics

Sonny Bill Williams says he told New Zealand coach Stephen Kearney he'd drop out of the Rugby League World Cup squad if his selection u-turn would hurt team harmony.

Williams also confirmed yesterday he plans to return to rugby union in New Zealand in 2015 ahead of the All Blacks' Rugby World Cup defence after completing a second season with NRL premiers the Sydney Roosters next year.

He will also put his boxing career on hold to focus on getting to the Olympics with the New Zealand rugby sevens side in Rio in 2016 - "I won't have the time to box in the next three years."

Williams' decision to make himself available for the Kiwis' World Cup title defence meant Tohu Harris was dumped from the New Zealand squad by Kearney to accommodate the cross-code superstar.

"It was a difficult situation coming in with the whole Tohu thing, and I feel very remorseful," Williams said at the Kiwis' team camp in Sydney.

"But I didn't want to look back in 10 years at something that I would have regretted.

"When it first came out, I said to the coach I am willing to drop out because I felt that bad.

"But he told me I had the backing of the senior players and now I just go with the coach's decision."

Speculation was rife on Thursday that Williams was returning to Super Rugby with the Chiefs next year when he was spotted signing documents while lunching with team officials and senior management from the NZRU in Sydney.

But 24 hours later, the Roosters confirmed he was staying with them for another year and Williams said the documents were a declaration of interest in returning to rugby in 2015.

"It was making my intentions clear; the deal hasn't been done yet. I was clearing up a few things and being up front and honest with them," he said.

"It's how I've always been and my year here at the Roosters couldn't have gone any better.

"I know people will take it the wrong way but I can't worry about that ... I had to do what felt right in my heart and my gut."

Williams said when Kearney contacted him 24 hours after helping the Roosters beat Manly in the grand final, he was leaning toward going back to rugby union and didn't feel he should play the league World Cup in that case. But the prospect of becoming the first man to win a world title in rugby union and league was a challenge he couldn't miss.

- AAP