If Japan is worried about China's growing economic and military clout, its Deputy Foreign Affairs Minister Koro Bessho did not show it.

In an exclusive interview with The Nation's editor-in-chief Suthichai Yoon over the weekend, he reiterated that his country did not see Beijing as a threat, but rather as a big neighbour who's taking a more assertive role in the region. But this big neighbour and everyone around would be better off if there was a greater degree of transparency in crucial foreign policies.

"Saying that a problem or conflict exists is very different from saying that someone is a threat. I don't think China bullies us, but I would agree that the Chinese are getting to be more assertive. And that is something that the international community has recognised and has asked China to play a role (accordingly) - an important role that they can perform," he said.

The Japanese deputy minister was in Bangkok last week and met Sihasak Phuangketkeow, the permanent secretary of the Foreign Ministry. The trip followed up on Prime Minister Yingluck Shinawatra's official visit to Japan in March, when several important agreements were reached.

Bessho said Japan was aware of but not alarmed over developments in China including its military profile in the region.

"We certainly do not see China as a threat. What we are saying is that we would like China to be more transparent in their policies and their relationship with their policies, and the actual (scale) of their military build-up."

A Beijing-Tokyo maritime row erupted when Japan detained 14 Chinese nationals from Hong Kong who landed on the disputed Diaoyu/Senkaku Islands on August 15, in hope of asserting Chinese sovereignty. After detaining them, Japanese authorities quickly deported them. The incident ignited nationalistic sentiment across China.

"Our position is that there is no territorial dispute. We feel that we don't want the differences in our views or positions on this particular issue to overshadow the overall relationship," Bessho said.

"We have no reason to believe that the Hong Kong fishermen were backed by the Chinese government to trespass on Japanese territory," he said.

As this year marks the 40th anniversary of the normalisation of diplomatic relations between China and Japan, their leaders have agreed to strengthen a relationship that is mutually beneficial based on common strategic interests.

However, there have been better days in the bilateral ties.

"Between the mid-1980s and now, we do see the decline of the warm feelings that we had enjoyed in the 1980s," he said.

He was quick to add that Japan's nationalistic sentiment had other factors including the bursting of the bubble in the 1990s, which coincided with the declining birth-rate, which aggravated the situation of an ageing society, and, of course, the great natural disaster (tsunami) last year.

"People are feeling a little less optimistic about the future. I think people are beginning to look inward. What we want to do is to be more outward-looking," he said.

Asked about the US rebalancing strategy in the Asia-Pacific, he said: "We all welcome that, including China, including Southeast Asia and of course Japan.

"Their [the Americans'] interest is important for us and Asean countries. We want to secure stability in this region and I think it's the same for China, which is so essential for economic development," he said.

In terms of Asean+3 (10 Asean countries plus China, Japan and South Korea), he said the plus three nations had played a very important role and achieved some important cooperative targets.

"What Japan wants to do is to come up in the end with a free-trade agreement for all [the] Asia-Pacific. That may be the ultimate goal," he said.

"We have enough experience, technology and strong partnership with our friends. We can play a role that could help build and cement a solid and stable platform from which we can all benefit," he said.

In regard to North Korea's missile programme, he said: "What we would like to see is for North Korea to show us that we can believe in them and that we can establish a relationship of trust.

"The starting point is for them to honour their past promise. I think that'll be the most important point," he said.

Asked what might be Japan's biggest concern from a foreign policy viewpoint, he said: "North Korea certainly is considered a very important issue. But in order to deal with this issue and any other flash point, I think it's important to (solidify) a regional structure that can deal with them (peacefully).

"As for the structure we already have in hand, what we want to do is make sure it can actually function."