Rugby World Cup 2019: Jacinda Ardern using sport's diplomacy to strengthen Japanese relationship

The Prime Minister is using rugby diplomacy to strengthen our relationship with Japan.

There's concern New Zealand has let it slip in recent years in terms of trade and tourism, but it was a slip of the tongue that's caught Jacinda Ardern out.

Ardern received a Japanese expression of their utmost respect to their guests, and it was a welcome for a jet-lagged Prime Minister.

"[I] just got in," she told reporters.

For a moment on Wednesday night, Ardern wasn't sure where she was.

"This is an incredibly exciting time for New Zealand and its relationship with China," Ardern said before correcting herself. "Sorry excuse me, Japan."

It was an innocent mistake that unfortunately came amid concerns that New Zealand's relationship with Japan has drifted in favour of China.

New Zealand exports to China have soared since 2008, but they've been stagnant to Japan until this year.

Meanwhile, Japanese tourist numbers are still well below where they were in the early 2000s.

"There is an opportunity now on the back of particularly the popularity of the All Blacks here in Japan, to entice even more people to come and visit our home," Ardern told reporters.

Rugby diplomacy coming into play - as Ardern looks to strengthen ties on trade and tourism, while working on a pact to start sharing classified information.

"This will make it easier for us to deepen those ties, [and] continue to work together in what is quite a volatile regional security environment," Ardern said.