TOKYO (DPA) - New Zealand Prime Minister Jacinda Ardern's four-day visit to Japan started out on an awkward note when the politician mixed up China and Japan in a press conference on Thursday (Sept 19).

"This is an incredibly exciting time for New Zealand and its relationship with China, sorry excuse me, with Japan," she said in her opening remarks.

While Ms Ardern reportedly blamed jet lag for the mix-up, it comes a day after the Asia New Zealand Foundation report claimed that the Pacific country's relationship with Japan was overshadowed by China's economic power.

"As China has risen in economic might, and growth in other Asian countries offers new potential, the strength of our relationship with Japan can be easy to overlook," the report says.

After a meeting with Japanese Prime Minister Shinzo Abe, Ms Ardern said the countries - which both lie on the volcanic Ring of Fire - agreed to further strengthen their Strategic Cooperative Partnership.

"Japan is increasingly one of New Zealand's most important partners in the world," Ms Ardern said.

"In a challenging and changing global and regional environment, New Zealand and Japan enjoy a stable long-term relationship that in recent years has gone from strength to strength."

She added that Japan is New Zealand's fourth-largest trading partner and "an important source of high quality investment".

Ms Ardern, who is in Japan to discuss trade and tourism, also thanked the people of Japan for looking after New Zealand's rugby team the All Blacks and their fans, with the Rugby World Cup kicking off in Japan on Friday.