New Zealand coach Steve Hansen has admitted he is "disappointed" that Richard Kahui did not reveal his plans before departing Waikato to join Japanese side Toshiba Brave Lupus.

Kahui has already agreed a deal to sign for Toshiba at the end of the season, but his national team boss has revealed his frustration.

"We were very disappointed with that because he didn't really speak to us, or his agent didn't. I always find that a bit frustrating," Hansen told Sky Sports News.

"Normally you hear from them, then you've got an opportunity to discuss it, and put a reasonable offer and if you want them to stay you've got an opportunity to fight to keep them. In this case we didn't so that was a bit disappointing. But we've discussed that and moved on."

Kahui is understood to be keen to return to New Zealand ahead of the 2015 World Cup.