Against the wishes of many business groups, the New Zealand government plans to ratify the accord in August and this week signalled a new carbon tax to help curb its greenhouse gas emissions to 1990 levels.

Japan, the world's second-largest economy, strongly backs the protocol signed in 1997 which Washington shunned saying it would hurt the U.S. economy.

"We are making efforts to ensure that the Kyoto Protocol will be ratified in the current session of Diet (Japanese Parliament)," Koizumi told reporters through an interpreter.

"New Zealand has also shown much interest in the global warming issue...so we believe we can make further progress on cooperation on this issue," he said.

But the two prime ministers ruled out any chance of a free trade agreement, after Clark sought one during a one-hour meeting in her official residence.

"New Zealand stands ready to discuss such an agreement when Japan is ready. Right now Japan is not ready to discuss a free trade agreement with New Zealand, which would have to include agriculture," Clark said.

Koizumi has proposed closer ties with Southeast Asia, ultimately leading to the formation of an East Asian cooperative community that could include Australia and New Zealand.

Japan bought around NZ$4 billion ($1.80 billion) worth of New Zealand goods in the year ending February, compared with exports to New Zealand of NZ$3.6 billion.

However, Koizumi was not specific on how New Zealand could be included in the community, which he stressed must take into account "global perspectives".

Clark has described New Zealand's relationship with its third largest trading partner as one of its most important, albeit with some points of difference, among them whaling.

New Zealand and Australia plan to renew their bid to set up a South Pacific whale sanctuary at a international whaling meeting in Japan later this month.

Clark registered New Zealand's difference of opinion on whaling and said that she would have preferred Japan supported the sanctuary.

Japan opposes the sanctuary and will instead seek to end a 16-year ban on commercial whaling at the International Whaling Commission annual meeting in the Japanese city of Shimonoseki beginning May 20.

"We are fully aware of New Zealand's position regarding whaling....but this position will not impede the good relations we have between our two countries," Koizumi added.