New Zealand PM mistakes Japan for China

New Zealand PM Jacinda Ardern has blamed jetlag for a gaffe on her first official visit to Japan.

Ardern had only just arrived when she said it was an "incredibly exciting time for New Zealand in its relationship with China – excuse me sorry, with Japan".

When asked later about the error, Ardern said: "You'll understand I've been on continuous travel and just this moment I stopped here."

Ardern is in Japan to discuss trade and tourism with prime minister Shinzo Abe. She will also watch New Zealand at the Rugby World Cup.