Prime Minister Jacinda Ardern and her Japanese counterpart have agreed to share information classified up to the level of "top secret".

In bilateral talks last night with Fumio Kishida, the PM agreed to enhance intelligence-sharing to bring the countries closer on international security issues.

The Prime Minister addressed media today in Tokyo, on the second day of her visit to Japan.

She said she and Kishida had a warm bilateral discussion.

"It was substantive and in the end an hour longer than we intended for the bilateral and dinner to extend for.... a reflection of the relationship that New Zealand and Japan has, but also our strong shared interests."

Ardern said shared bilateral concerns were also discussed, especially the war in Ukraine.

She said bilateral information exchanges were also discussed. An example of useful information-sharing was after the volcanic eruption in Tonga earlier this year, when satellite imagery was shared.

Development in the Pacific was also discussed.

"Japan has long been a source of high-quality infrastructure in the Pacific," Ardern added.

Asked about the Pacific and its possible militarisation, the PM said for New Zealand, the focal point for every bilateral and multilateral deal had to be regional security. "No-one wants escalation."

The PM said New Zealand would benefit from sharing information with Japan on Pacific affairs.

She said the information-sharing agreement with Japan could include information classified up to the level of "top secret".

"These are not unusual for either country, and we do already share information."

A similar bilateral information-sharing deal exited with Spain already, Ardern said.

"They're not just about security and intelligence."

Asked if the deal was a reaction to China's increased assertiveness in the Pacific, Ardern said: "We call for all countries to uphold international law in our region."

Ardern said the Japan information-sharing deal was not influenced by the AUKUS defence agreement involving Australia, Britain and the United States.

New Zealand had these kinds of arrangements with a number of other countries, so it would be odd not to have such an arrangement with Japan, Ardern added.

New Zealand maintained its sovereignty over information-sharing and it was not necessary to consult with Five Eyes partners about the Japan arrangement.

Ardern and Kishida also welcomed the Biden Administration's Indo-Pacific Economic Framework initiative, a US initiative to step up engagement in the region while the US joining the CPTPP trade agreement is off the table.

But both Prime Ministers also "expressed their strong and shared desire for the United States' return to the agreement".

Ardern said the trip would also highlight the importance of people-to-people exchanges and homestays.

"They stand us in really good stead in the future."

The PM said she was 10 years old when her family hosted Japanese homestay students in Morrinsville. Ardern was going to have a reunion with a homestay guest shortly.

On international education, the PM said border re-openings were happening in phases but there was a substantial lead time for someone deciding to visit New Zealand for a long stay.

Ardern was asked about the extradition of Kyung Yup Kim, a New Zealand resident accused of murder in China.

She said local courts had rigorously followed the case. Asked if she was confident Kim would get a fair trial in China, Ardern said: "All of these questions have been raised and considered as part of our courts' consideration of the extradition."

'The world is at a crucial moment'

Ardern arrived at the Kishida's office and residence last night to a formal welcome. She inspected the Guard of Honour before sitting down for formal bilateral talks, which she opened by emphasising the shared values of both nations and their support of a rules-based global order.

Kishida, in his opening translated remarks, said the Russian invasion of Ukraine had "shaken the very foundations of the international order, and I want to work closely with New Zealand to take resolute responses".

And in the press conference afterwards, he said: "The world is at a crucial moment."

Ardern and Kishida's joint statement committed to starting negotiations on a legal framework for the "reciprocal protection of classified information exchanged between the Governments", so it can be seamlessly shared.

"This will support closer engagement and support peace, stability and security in the Pacific and the wider Indo-Pacific region," Ardern said.

Their joint statement didn't name China, but the leaders also "reiterated the need to address growing strategic challenges in the Pacific that could destabilise the regional security environment".

It follows the signing this week of the China-Solomons security pact, which has led to increasing concern about the possibility of Chinese military presence in the Pacific - though China and the Solomons insist it poses no threat to the region.

Japanese Prime Minister Fumio Kishida. Photo / Pool

Ardern and Kishida noted the 70th anniversary of diplomatic relations between the two countries, and agreed on further areas of collaboration including trade and sustainability.

Trade between New Zealand and Japan has soared with the CPTPP, which has given New Zealand exporters far greater access to Japanese consumers. A 2019 Asia NZ Foundation-commissioned report said that, by one estimate, 80 per cent of the value of CPTPP to New Zealand comes from improved access to the Japanese market.

"I highlighted to Prime Minister Kishida the high-quality goods and services that New Zealand's exporters offer Japan, particularly in food and beverage and technology," Ardern said.

"We also noted the close partnerships between our businesses in renewable energy and the scope to build on these."

Ardern also announced a New Zealand government investment of up to $8 million into joint research on Advanced Technologies, including renewable energy.

Prime Minister Jacinda Ardern and Trade and Export Growth Minister Damien O'Connor with the Kiwi Brothers at a Zespri promotional event. Photo / Supplied

Earlier yesterday she launched two renewable energy New Zealand-Japan initiatives, the first one around hydrogen-powered EVs, the second around developing geothermal energy.

The initiative will feature a fleet of the Toyota Mirai being shared by eight New Zealand companies in a car-pooling trial - the Warehouse, Air New Zealand, Saatchi & Saatchi, TVNZ, Beca, Westpac NZ, Spark, and Z Energy.

She also visited a promotional event for Zespri - Japan is a $750 million market for Zespri - where she tried her hand at Japanese calligraphy, posed for photos with the famous mascots the Kiwi Brothers, and watched Trade Minister Damien O'Connor decorate a pavlova with kiwifruit.

Today is her final day of scheduled events in Japan.