Former UN secretary general Ban Ki-Moon hailed tourism as “an important vehicle for promoting understanding”.

He told the Pacific-Asia Travel Association (Pata) summit in Gangneung, South Korea: “If there had been opportunities for people to travel freely to North Korea, it would have changed years ago.

“That is the genuine power of tourism, not sightseeing. Imagine demarcation lines gone and people could travel freely – you would see faster change.”

Ban Ki-Moon said he was “moved and encouraged” by the talks between North and South Korea and the planned summit between North Korean leader Kim Jong-un and US president Trump.

He said: “I hope the summit will make good progress, but it is just a beginning. We should not be overly excited when have been disappointed so many times.”

He described North Korea’s cancellation of talks with South Korea this week as “a source of deep concern” but insisted: “I am much more hopeful than at any time before.”

Asked about the prospects for the summit with Trump, he said: “They are two leaders with very different styles, but they are both sometimes unpredictable. If they take a strategic decision, they can make a big deal.”

Ban Ki-Moon led the UN for 10 years to December 2016. He said: “During my time as UN secretary general I prided myself on recognising tourism as an important vehicle for promoting understanding and mutual respect.”

He referred to “the alarming rise in racism and xenophobia worldwide”, but said: “At the same time, this is one of the best times to be alive.”

Asked about his achievements as secretary general, Ban Ki-Moon identified the Paris Agreement on Climate Change and the UN Sustainable Development Goals.

He said: “The Paris Agreement [in December 2015] took 23 years. We had 195 countries [sign the agreement]. Just one country could have killed the decision.

“The UN Sustainable Development Goals are the most ambitious and far-reaching vision the UN has ever presented. We can’t negotiate with nature.”

His biggest disappointment, he told the summit was that “world leaders do not act like leaders”.

“When they come to international conferences they always talk loud, saying ‘I will do this for humanity’. When they fly out they become national leaders.”

He said: “I urge world leaders – don’t build walls, erect bridges.”