Wellington - Two-time Rugby World Cup-winner Dan Carter said on Tuesday was planning to return to Japanese club rugby after a bid to rejoin French club Racing 92 ended when he was ruled medically unfit.

Carter said the problem was a bulging disc in his neck which might require surgery but would not stop him playing rugby.

The 37-year-old, who earned 112 caps for the All Blacks, said while French authorities were especially strict about medical clearances, he would still be able to play in Japan.

Carter helped his Japanese side Kobelco Steelers to a Top League title last year and is still contracted to the team.

"The beauty is that my second year in Japan doesn't start until after the World Cup," he told the New Zealand Herald.

"The Top League season there has been pushed back because of the World Cup, so I will have plenty of time to spend with my family. I thought I would get my body ready for my second season in Japan." 

The World Cup, hosted by Japan, ends in early November.

Carter was poised to rejoin Racing 92, where he starred from 2015-2018, on a short-term deal after ex-South Africa flyhalf Pat Lambie announced his immediate retirement due to multiple concussions.

He described the medical knockback as "a blessing in disguise" which would help him prepare for his eventual retirement.

"I get to spend more time back here in NZ," he said.

"I don't have a lot of rugby in me but I'm still loving it and enjoying it, so I guess this long break has helped me to phase into life after rugby."