BUSAN - South Korea has reiterated hopes for North Korean leader Kim Jong Un to visit the southern port city of Busan as an observer for a special summit involving all 10 Asean nations, just as a 40-day countdown to the event was launched.

Busan mayor Oh Keo-don said at a media conference on Wednesday (Oct 16) that Busan "wants to be the city to host Kim Jong Un" and lay a foundation for peace on the Korean peninsula.

He recalled how Busan "gave a warm welcome" to a North Korean delegation years ago, and added: "I think there is some possibility of Kim Jong Un visiting this time around."

Mr Lim Sung-nam, South Korea's ambassador to Asean, said a visit by the North Korean leader will be "very meaningful and will continue the peace process on the Korean peninsula".

He also noted that Asean holds a special key to North Korea, with two Asean countries - Singapore and Vietnam - having played host to summit talks between Mr Kim and United States President Donald Trump.

For now, Mr Kim's visit is "neither guaranteed nor completely out of the question", said Mr Lim.

The hopeful message came as South Korea launched the one-time Asean-Korea Train travelling towards Busan in the lead-up to the Asean-Korea Commemorative Summit, which is expected to draw leaders from all 10 Asean nations.

The idea to invite Mr Kim to the summit was first mooted by Indonesian President Joko Widodo last year, and Mr Moon welcomed the suggestion.

South Korea's intelligence agency last month raised the possibility of Mr Kim's visit to Busan, but experts said chances are low unless progress is made on stalled nuclear talks with the US. Inter-Korea ties remain frozen as well.

Slated to be held on Nov 25 and 26, the Asean-Korea summit celebrates 30 years of dialogue between the two sides.

Bilateral ties have deepened since South Korean President Moon Jae-in introduced the New Southern Policy aimed at increasing collaboration with Asean to the level of South Korea's four major partners - US, China, Japan and Russia.

He completed his promise to tour all 10 Asean nations last month, reaffirming his commitment to the region.

Bilateral trade hit a record-high of US$160 billion (S$220 billion) last year, with Asean becoming South Korea's second largest trading partner. The two sides hope to increase two-way trade to US$200 billion next year.

Asean has also become South Korea's biggest tourist destination, with more than 7.9 million South Koreans travelling there last year. Tourists from South-east Asia to South Korea, meanwhile, totalled 2.4 million last year.

Ambassador Lim noted that bilateral trade has increased 20-fold in the past 30 years, while tourism has boomed 100 times.

"Going forward, we hope that Asean and Korea will have 20 times more trade and 100 times more people-to-people exchanges, until we become essential partners to each other," he said.

South Korea already has a free trade agreement with the regional bloc. Plans are underway to conclude individual deals with Indonesia, the Philippines and Malaysia.

Myanmar's ambassador to South Korea U Thant Sin hopes the two sides can come up with more concrete guidelines for the New Southern Policy during the summit.

"Then we will both feel that we are important to each other," he added.

Wednesday's train journey drew 200 participants, including ambassadors from all 10 Asean countries, government officials for trade and arts, young people, performers and media.

The train made a stop at the ancient capital city of Gyeongju, where participants visited the Bulguksa temple.

The train will also stop at Suncheon and Gwanju on Thursday before returning to Seoul.